Has anyone here done a joint birthday party for their kids?

Our boys birthdays are a day apart in May and it just seems like a lot of work to do two birthday parties for them. Especially because our eldest doesn't exactly have any friends.

In the past we've just done a family affair at my IL's, which always works out great and we'll hopefully ( I have to talk to her) do that again this year. However, I want to be more involved this year in planning and decorating and stuff.

So anyway, my question is how can I do a joint birthday party for a 6 & 9 year old that still makes each boy feel special??

I know joint birthday parties can suck sometimes but we really can't afford to be throwing them two parties. In fact, they already get two, one at their moms and one with us. (Their mom is so uncooperative we really can't collaborate anything with her).