Hi Elisa! I am a huge fan of character meals. I don't like to waste time in the theme parks standing in line to see the characters -- it's so relaxing to have them come right to our restaurant table and pose for photos or sign autographs. For me, being able to interact with the characters at a meal is well worth the cost. Because both of your children are under three years old, they will be able to eat free at all the character buffets, such as
Chef Mickey's or the
Cape May Cafe. A character meal would be a good way to introduce your children to the characters, and you'd have to pay only for your own meal at a buffet. The breakfast buffets are the least expensive character meals, so you may want to book one of those.
Your question reminds me, however, of the first time I took my son to Walt Disney World. He was about the same age as your youngest, and I had booked character meals for every single day of our vacation. Imagine my surprise at the first character meal when we learned that the sight of those characters terrified him! He screamed and cried every time a character attempted to get close to him, and I regretted making reservations at so many character meals on that trip. Since you're not sure how you're kids will respond, I definitely wouldn't book more than one character meal for this trip.
In answer to your other question, at the table-service restaurants, your children may eat free off of your plate, or you can purchase a kids' meal for them to share. Sharing is definitely permitted!
Hope you have a magical time!