Should I keep the money given to me by my abusive father or give it back?

When I was a kid, my dad was an abusive alcoholic. My sister and I were even put into foster care until we turned 18. He stopped drinking but he's still not a good person and is still verbally/emotionally abusive and I don't want him in my life or my son's life. I cut him out of my life 2 years ago. The rest of my family is still on good terms with him and always invite him to our family get togethers like birthday parties. I do my best to avoid him at these events. My birthday was this week. My sister insisted on having a party for me last weekend like she does every year. I didn't know until I got there that she invited our dad. I know she always invites him to everything but I really didn't think she'd invite him to MY birthday party. She knows how I feel about him. She knows I don't want to see or talk to him. She didn't invite him to my last 2 birthdays so I don't know why she did this year. I really wanted leave as soon as I found out he was there but didn't want to make a scene or be rude to the others. My dad bought the birthday cake. And he gave me a card with $40 in it. The very next day my dad came over to my house "just to say hi" and chit chat. He gave me another $20 because this was my actual birthday. I couldn't say anything to him then either because he brought my niece with. Although I probably wouldn't have said anything even if she wasn't there anyway. Even though I'm an adult now I'm still afraid of him. When he's around it's s like I'm child again. I think that since he came to my party and I didn't say or do anything about it and also because I accepted his gift that he now believes that we have made up and we're all good now. But that's not the case and I still want nothing to do with him. I think I should give him the money back that he gave as a birthday gift. And maybe even pay him back for my birthday cake. But I never have my own spending money like this. Advice please? Should I send him the money back to make sure he knows I don't want him in my life? Or should I just keep the money? I also don't know what say or do about my sister. I haven't talked to her since the party. I really want to tell her how I feel but I don't want to start a fight. Me and my son are supposed to go on a 3 day vacation with my sisters family in a few weeks. I haven't had a vacation trip in about 15 years. And my son has never been on a vacation. We're both really looking forward to it. So I don't want to fight with my sister and mess this up. We wouldn't be able to go on vacation without my sister. What should I do?

I guess I would say the money and birthday cake is really the least he could do for you, and I'd accept it as a start. It doesn't make up for things, but at least he remembered your birthday and made an effort to be present for it. I would just try to stay on neutral terms for now, and if you don't want him around in you and your son's life that's fine. You can have a discussion with your sister at some point about how you weren't comfortable with her decision to invite your dad to your party. But I would try to be on good terms for now so you can enjoy the vacation, so long as your dad has no part in the vacation yet. What I've learned is that you can't really control some things, including what family members insist on doing. Sometimes if you talk things over and have a discussion they'll hear you out and be aware of your position, even if they might not fully understand it. It may be a case of "Sister knows best", and she might try to constantly play miracle worker and bring you and your father closer. Or maybe it was just an issue she overlooked while planning things, or something she didn't view as being as big of a deal as you do. Either way you are an adult now, you have your own family and you shouldn't let your father's actions eat at you. Try your best to play nice and keep moving on.