Hi Peggy! I'm loving your questions! Your granddaughters are going to have the best trip ever! I'm a huge fan of character meals - you get to enjoy a delicious meal and, the best part, they're an excellent opportunity to spend quality time and get great pictures with your favourite characters. that being said, Tink and Rapunzel are better spotted at character meet and greets in the Magic Kingdom.
Tinkerbell and her fairy pals have their own magical spot at
Tinkerbell's Magical Nook, located in Adventureland. I would try to get there early in the day, as the line up can get long. Rapunzel meets her fans along with the other princesses at the Fairytale Gardens. Times do vary, so be sure to check out the Magic Kingdom Times Guide.
Two great princess character meals are
Akershus Riyal Banquet Hall in Epcot's Norway and
Cinderella's Royal Table in the Cinderella Castle in the Magic Kingdom. Both of these are perfect for your little princesses. Princesses at each vary, but they'll meet several at either spot. Be sure to book in advance, as they fill up quickly!
Hope this helps Peggy. Keep the questions coming as you think of them!