Trish,
I agree TOTALLY with Boppie, Steve, and Jan. NO way should you even be worrying about juggling hostess duties so soon after surgery (and maybe before you even come home from the hospital!). You need to keep things very simple, so you can focus on your own recovery and getting stronger. If you want to have your mom with you, you definitely should!
Do your in-laws know/understand about your situation? Maybe they don't realize that though you have a good prognosis with an AN, it is still brain surgery and comes with a necessary recovery that varies in length for different people? If not, maybe your husband could explain a bit more to them, and suggest that if they stay at a hotel, that may be the best of both worlds--they'll get to meet Cali and provide you with needed babysitting help, and also meet your mom.
If they're reluctant to stay in a hotel, and you're not able to/comfortable with rescheduling your surgery, another possibility would be to see if your in-laws can reschedule their trip. Airlines can be quite sympathetic about changing flight dates for health issues (and "brain surgery" has a serious enough ring for them to be quite accommodating, I suspect). I've had airlines reschedule for health related reasons--both my own and my mother's--on at least four occasions, and I never so much as paid a penalty for changing the date of my flight!
Good luck sorting this out!