Hey Teri!
I am so excited for you! I still feel that excitement every time I plan a trip to Disney. Soon, you and your loved ones will be standing on Main Street in the Magic Kingdom looking up at Cinderella's Castle, and that moment...the exciting butterflies in the tummy moment...that is the moment that brings my family back to Disney every time!
Ok...on to your questions! Character Dining is a lot of fun and the cost varies with each location and depending on if you are going for breakfast, lunch or dinner. If you check out AllEars.net they have menus listed AND recent costs for each! It really can vary from around $20 to almost $60 for adults and children (ages 3 to 9 are considered children in Disney) from around $10 to $30. Those are total ballpark figures and can change!
A great first time character dining for a nice price is Cape May Breakfast Buffet at the Beach Club Resort. Kids are around $10 and adults around $19 for the full buffet. The buffet is incredible with something for everyone from fruit, bagels, eggs, bacon, biscuits to MIckey Mouse waffles!
You can bring snacks and water into the Parks.
You can leave for a break and return to the same Park.
Teri, I so hope that you and your family have a magical time! Please let us know if you have any more questions.