Hi Belle! You're going to have a great time! It'll be my 10th time this upcoming January and I learn new stuff every day here. As for ride opinions, at your children's ages, I was still very much into Fantasyland (when am I not?) but I was also old enough to really love and enjoy the Haunted Mansion (but I think this can definitely scare many kids, so only you can judge that one - it scared the heck out of my 21 year old friend Pat!), all of which are in Magic Kingdom. Journey into Imagination at EPCOT was also a big love, and still is. I'm sure all of our other wonderful posters can give you many more ideas than I can, though.
All in all, I hope you have a wonderful time here and at the World!