Should I become my mother and her boyfriend's rep payee again?

Ten years ago, I decided to become my mother and her boyfriend's rep payee. Both of them are in their late 60's and both are severe alcoholics. While I was the payee, they were evicted out of several apartments due to unsanitary living conditions, and the final straw was when one of their friends died on their floor from a drug overdose. Mom was drinking one night and fell, causing her to fracture her leg. She spent time in a nursing home and didn't have a drop to drink the whole time she was there. I was surprised because she said she didn't miss it. As soon as she got out, her boyfriend brought beer and she relapsed. I have a family myself and enough stress as it is and they put a lot of stress on me on top of what I already have!

 I was talking back and forth with my sister and she decided to take them a few states away closer to her and take over being their rep payee. A couple times a week she'd drive over and check up on them but she would not give them any beer money. She pays their bills and gets them food but she refuses to give them not even a few dollars for beer money. She told him to go beg for it and she's not contributing to their addiction. Well all hell broke lose and they accused my sister of stealing their money and even called social services on her.When I was their payee I actually did give them extra money left over after their bills were paid,but it was never enough and they moved some drug addict into the apartment for $300 a month to fund their alcohol addiction back when they were here with me. 

Fast forward two years after they moved near my sister and now my sister is the bad guy and mom curses her out because she won't cave in and give them booze money. Now my sister is asking me to become the payee again. She says she's tired of being disrespected , doesn't want to be the bad guy anymore and she's tired. But as a rep payee, I would be responsible for paying her bills online and if they have money left over, I'd have to do a Western union transfer to my sister since they can't spend money responsibly.That means she would go grocery shopping for them and send me the receipt. I've met my sister once in my lifetime and no, I really don't feel comfortable transferring money that's theirs to my sister not knowing 100% of the story about the theft accusations. Anyway, as a rep payee, I should be handling the money, not someone else.

 I was thinking about getting my sister to hand it over to a rep payee organization, but if they are going to hand mom and her boyfriend a check after the bills are paid, and they need this money for food, who knows if they will use it for food. They could blow it in 2 days on beer! Also my sister plans on moving out of state within the next year or so. If that happens, she may leave mom and the boyfriend behind. I really don't blame her, but I also don't want to deal with this problem again! Part of me want's to help but part of me want's to stay far away! What would your do? I'd love to know! Also, does anyone have experience dealing with a payee organization? Thanks for your answers!