The husband needs to take charge of this - if he wants the RSVPs to come to you so the birthday girl doesn't see them, that's one thing. But he absolutely should know her better than anyone, and he should know what's up with the friends. I'm not sure why there's someone in "the group" that she doesn't like - it's time for someone to draw a line in the stand about social engagements with people you don't like. But the husband has to take on the invitations so it's not your fault about who gets invited or not.
I think her husband needs to decide that he is giving her a small dinner party with just a few couples that he knows she likes, and not make it a big party of 40 people that leaves out just 1 person who's a pain. Part of the problem with bringing up kids who are taught they need to invite the whole class is that they grow up and are afraid to make a decision about who they want to party with. The husband needs to face facts here.
Your job is to be the support system for him and maybe field the RSVPs, and maybe help plan the menu or buy the paper goods. I'm not sure how he's planning to surprise her and bring in the food - is it at someone's house (his? yours?) or at a restaurant?
I think he really better know his wife and all her friends really well before he hires a stripper. I've seen too many parties with people cringing about this. If he's inviting people from her job or his, that's a huge no-no. Is he doing it because he really thinks she would just love this and he would enjoy watching her love it? Or is he clueless about what people in the group will really enjoy? If it's something everyone would dearly adore, and not find embarrassing or exploitative, fine. If there's a question, then go for a safer alternative.
One thing we've done for 40th, 50th and 60th birthdays is to have a bit of a "roast" - we ask guests to bring a little something, like a poem, limerick, funny anecdote, or even a song (lots of people rewrite the words to a popular song or old standard, and hand out song sheets for everyone to join in). It's half funny, half touching, and a great way to say how much you like the honoree. When there's a combination of guests from someone's social group, neighborhood, family, old friends, and work, fine. We've also done photo boards of pictures through the ages, or a slide show on the laptop. And this becomes the entertainment, so no stripper is needed.
You know your friend, and ideally the husband does too, and this party will be about HER and not some crazy idea of what he thinks is "required" for 40th birthdays.
I think you and he need to get on the same page, or you need to just take on what you can and would like to do, and leave the rest to him. He can hire a party planner and a waitress/caterer if he wants to.