Hi, Melissa:
The opening words in your post probably explain most of the problem.
That less-than-great relationship with your mother and sister-in-law you mentioned indicates that they probably have little interest in doing you the favor of watching your children while you're in the hospital. It's likely an imposition on their normal schedule. Because you're not ' close', they're complaining about it - but using the cover of asking why you didn't have radiation, etc. Of course, minus the hospitalization, they wouldn't be asked for child care assistance so their questioning of your decision is another way of saying
"why didn't you do what would be more convenient for us?". Ouch.
Unfortunately, this blatantly self-centered attitude is all-too common, even within families. Sometimes, relatives, especially in-laws, are the least sympathetic to your needs. Still, as you noted, you
will need their help. I hope I'm not stepping on any toes here as I don't know your personal situation, but it might help if your husband could try to explain to them (they
are his family) that this is serious surgery and that you need to know your children are in safe hands. This is asking for a little sympathy for your situation but also flatters them, to some extent. If possible, he needs to step up here to help make this situation go smoother and spare you the stress of dealing with the recalcitrant in-laws during a time of need. Remind him that you're having brain surgery within a month and you could sure use some help. In-laws attempting to make you feel guilty for having necessary surgery (that no one looks forward to) because they really don't want to watch your kids, does not qualify as 'help'.
Again, Melissa, I'm unaware of any family dynamics that might make this suggestion moot or somehow inapplicable to your situation but it was the first thing that sprung to mind when I read your post. I trust it'll be of some help and, if not, I'm sure others will come forth with other, possibly more useful advice. Meanwhile, know that you'll be in our prayers and that we hope this unpleasant situation will be resolved long before your surgery date. Try to stay calm and strong...for you and your family...and you'll do fine.
Jim