I took my daughter when she was 11 months, 2, 4, and 5, and my son when he was 1 1/2 and 2. We made some priority seating arrangements, mostly for character dining, which the kids loved. However, most of the meals we played by ear. It gave us flexibility (eat when hungry, don't plan the trip around meals).
Some of the places the kids liked that have PS are Cinderella's castle (be sure to call exactly 60 days before you want to dine-PS reservations opens at 7:00 a.m. ET and the reservations fill up within the first minute-you may have to try several days in a row), The Crystal Palace, Hollywood and Vine at MGM, Morocco at Epcot (daughter got to dance with the belly dancer-it was the highlight of her trip).
My daughter found Mexico at Epcot scary one trip but loved it a couple years later. It is dark and they have a volcano. Also the one at the entrance to AK (name is on the tip of my tongue) the kids liked one trip but found it scary on the next trip. Ah, I remember - The Rainforest Cafe.
You can also make PS the same day for a number of restaurants and if you are staying at the Disney resorts you can call PS from your room. This adds a lot of flexibility so you don't have to plan exactly which park to visit which day.