Kyla:
It is recommended that you make reservations for any sit-down restaurant at Disney (commonly known as table service). You can always show up for a standby table, but the wait for some of these restaurants without an advanced dining reservation can be well over an hour--or you may simply be turned away.
Because you are staying 14 days, my hunch is that you will not want to have all of your meals at the food court or the quick-service restaurants, nor would you like to have to wait an hour or more for a nicer meal. Definitely do a little research here at the Mom's Panel site under Table Service or my favorite Disney dining website:
www.allears.net and see what might work best for your family.
As for "not-to-be-missed" restaurants, I just asked my 5-year-old and he exclaimed, "Chef Mickey's!" It's not necessarily MY favorite because it is a little on the noisy side, but the buffet is extensive and the time with Mickey and the gang engaging. Rainforest Cafe and T-Rex are perinneal favorites with our boys along with Sci Fi Dinner Theatre where they get to eat in a car, Biergarten for its floor show, and Ohana with its limbo and coconut races.
I wouldn't recommend more than one table service restaurant a day, as you'll spend more time eating than enjoying your vacation. But make your reservations soon or you may find yourself coming back to our panel asking for advice on how to get a reservation at the more popular restaurants that are now full....
Wishing y'all a magical vacation!
Whitney