Your best defense against the flu is to eat healthy (avoiding lots of sugars that weaken the immune system), getting proper rest, avoiding stress and washing your hands diligently. That's really important for your 2 1/2 year old and even for your 10 month old if he handles toys that other kids have touched.
If you do decide to get a flu shot, make sure it does not contain thimersol (mercury) or aluminum. Both of those substances are toxic to your nervous system. And before you get the FluMist vaccine, take a look at this:
http://www.mercola.com/2003/oct/4/flumist_vaccine.htm
I've never gotten a flu shot and haven't gotten the flu for years. My husband always gets a flu shot and often has the flu. So, I've not seen any correlation that suggests that the flu shot is useful and that's substantiated by research which shows there have actually been more flu related deaths amongst the elderly since vaccinations have increased:
http://archinte.ama-assn.org/cgi/content/abstract/165/3/265
I think you're much better off spending that money on healthy organic fruit and some vitamin C supplements like Emer-gen-C.