About the passports - 10 weeks is cutting it very close but one cannot say because the wait time changes all the time. You can pay extra for expedited passports, but if she currently has a good passport in her name, I would consider waiting to change her name until after the trip. I have heard of people running into problems because their legal name does not match their passport. You have a lot of details to worry about already - why add to them?
No matter what - if she changes her name and applies for new passport, if it does not come through on time (you can pay extra to have them expedited) be SURE to bring extra documentation - birth certificates, marriage license, etc.
Legally - a passport MUST match a legal name, just keep that in mind.