No offense but asking for sexual favors that include other people for a birthday gift probably isn’t going to go over well. Have you ever guilt tripped a woman into doing something that she’s already angry and defensive about? They say there’s nothing like a pissed off woman doing something that you asked of her…angrily. If you want her to seriously consider doing anything hotwife related you should talk it out and explain what your fantasy entails and that you’re not interested in her having a gangbang but instead want to see her having fun and being pleasured by someone else. If you want to use your birthday as a way to have some hotwife fun here’s what you should do…for your birthday ask if she’ll role play some hotwife situations with just the two of you or indulge you in talking about it some more and make it a fun, sexy conversation with lots of love and support from you. She may never be interested in actually doing it or she may just need the reassurance that you’re really into it and won’t change your mind or judge her for it after the fact (post cum regret can be a real bitch). I would advise against asking her to jump right in as it’s unfair to her and unfair to the third as well.