At the Studios...make sure to do E.T., Shrek, Jimmy Neutron and the Woody Woodpecker Kids Zone/Curious George play area. At IOA, Seuss Landing will keep your child entertained for hours.
At IOA, I would recommend Thunder Falls Terrace, Mythos and Comic Strip Cafe. Circus McGurkus Cafe Stoo-pendous is fun since the trolley goes though the building but the food is rather on the lame side. At the Studios, I would go with Louie's, Finnegan's or Mel's...all good choices.
I just got back from Universal yesterday. We spent a week at the royal pacific and had a great time. Our kids are 3 year old duaghter , and 4 and 6 year old sons . One of the greatest highlights of the trip was the character breakfast at IOA with spiderman, cat in the hat, thing 1 & 2. All of my kids loved it, the food was very good, and it was not at all crowded - it is also very reasonable for a character meal. With tip, tax, 3 kids, and 2 adults we spent under $70.00. We made a reservation for the 9am seating (first of the day) on a saturday and we were the only ones in the place for the first half hour - the kids got the characters all to their selfs. The character interaction was amazing - tip bring an autograph book.
Plan a "water" day with suits. Fivals area is fun, curious george is great - lots of water activities. We spent a ton of the time in Suess area. When you get to IOA in the morning go straight to Suess area - everyone else will head the other direction to marvel area and you will have the run of the place.