Should I allow my daughter's friends to stay overnight (or longer) at dad's house?

I think it would be a shame if your daughter and her family miss out on normal visiting and socializing just because they are caregivers. They have needs too, and not everything can revolve around the dementia parent and his or her needs.

Is there some other reason you don't want the friends' visits? Such as, do they have rowdy friends who cause problems? Drugs, etc.?

You are right that a schedule is very important. My aunt (91) with dementia is also very social and loves people but gets very overwhelmed when too many people are in her home. My mother without dementia would also get anxious when large groups were gathered in her home. Most elders, with or without dementia, like small children, do better with a calm, orderly routine.
There are too many variables to know what affect the visit will have on your dad. I would say that since things are going so well it’s a lot to risk.
Could you care for your dad and give your daughter time to visit with her friends when they travel through? Perhaps they could stay at your home?

Since daughter is the one living there it is she and her family who would have to deal with any fallout from the visit- the choice should be hers.  Caregivers give up enough of their lives as it is, turning their home into a psuedo facility is just a recipe for dissatisfaction and eventual burnout.

We have allowed sleepovers and get togethers... trying to continue life in the real world. However, the first thing I do is educate. I have been very open with this disease with my girls (12 & 10 yrs old). They are protective of GMA and they know the noise level that will agitate her. I will be honest, my 10 yr old has had it the hardest. For whatever reason she is the one my mom would take out her frustrations on. It was mostly verbal and sometimes physical, no hitting... only grabbing. Still breaks my heart that my girls will not know their true GMA. So I educated them first. We talked, cried, and hugged. I did a lot of apologizing on my mom's behalf. I explained that this was NOT the GMA their brother had. (Son is 25). So I shared memories. Explained what the disease was doing to her brain. More hugging and crying. When mom would get agitated or physical, I would calmly go over... acknowledge mom's frustration... let mom "explain" (Mom speaks gibberish) why she is upset with daughter... daughter would "Yes, ma'am" her... by this point mom would be relaxing and daughter was able to step away to the safety of her room... then I would redirect mom to any activity or snack. Mostly a snack because I would put her medication in it for the agitation. Half a pill... just enough to relax, not knock her out. Once mom was ok, I would go check on daughter for some more hugs, crying, and reminding. Friends are also educated, not in as much detail as my girls, but we explained the noise level needed to be kept low. Anyone staying the night ALWAYS sleep behind doors with child protective locks or a baby gate at the door. Yes, it sucks to have to make these accommodations, BUT GMA no longer lives in our world... she lives in the dementia world. Maybe later I will regret putting my daughters through this, but right now it warms my heart to see how much they love their GMA. We are blessed that the agitation was not an every day thing. Mom is a very happy dementia person and that phase did not last long. My heart goes out to those who have to deal with agitation 24/7. May God give you the strength and resources to deal with that ugliness.

We live 90 minutes away from dad and daughter. Her in laws were just there for the 3 day weekend and I guess he did ok but he had met them before too (not that he'd remember, haha). The first time she asked her friend got sick and ended up not coming. I am just trying to think of how this would affect dad. But you are right about having them be able to socialize with their friends.

Unless these friends are terribly demanding houseguests, I don't see why their mere presence should disrupt your father's routine especially? People with dementia often meet new faces; as long as the established familiar ones are there too it shouldn't be a problem.

What are your concerns, specifically? What are you afraid might happen?

Since Dad is friendly, I guess I would ask just how friendly and if you don't think he would be harmful to guests, why not. We are talking about grown ups and as long as they respect his situation and don't get loud, shouldn't be a problem.

CBatty has some wonderful suggestions and experiences regarding visitors.

I think that your daughter can have some friends stay over night at her dad's house for one or two days as long as your daughter has educated them on what the visitors can and cannot do----such as: No DRUGS; DO NOT bring MORE BEER for her Dad to drink then what the daughter already provides for him; that if her Dad starts to become upset or agitated that is a signal for everyone to leave the room or the house and go elsewhere to continue the visit; DO NOT ARGUE with her Dad; that her Dad tires easily and does not have the mental capacity to play board games or card games like he used to; that if he wants to watch a certain TV show, then HIS preferences override those of any guests. Your daughter and her guests will have to be extra vigilant that any activity they do will not upset her Dad, but I think if everyone follows some guidelines, the visit might be a happy event.

Also, don't be surprised if her Dad becomes disoriented or agitated or has a decline in physical, mental, emotional or psychological function AFTER THE VISIT. People with dementia tend to experience these temporary declines after they experience a situation that is DIFFERENT from their daily routine. Give her Dad time to "recover" from the visit before having more visitors.

Yep. Same guy. But since 4 years ago he had a car accident, lost his license and now we control his beer (as best we can) to 2 a day. So, he isn't getting drunk and becoming belligerent like when he was drinking 12 a day.

It depends a lot on who the visitors are and how they react. When we had my MIL at our house for most of of her last year, we found that some visitors were calm and OK, and some would wail and get upset at MIL's failing health and wail about how terrible she was looking.