We just got back from WDW and our youngest DS is 18 months. Surprisingly, he liked trying to color when we went out to eat. He doesn't like to color at home, but he enjoyed it at WDW. Maybe it's because he wanted to do what his older siblings were doing.
In addition to coloring, I had a few small quiet toys and a container of Cheerios in my bag. That's all we really needed. He did get a little restless toward the end of one meal, so DH took him for a little walk. Other than that, he did fine. We ate at Boma, Brown Derby, Jiko, Spoodles, the Plaza, Kona, Tusker House, & Crystal Palace with no problems.
One word of caution if you're doing character meals, don't let the characters get too close until you can see how your baby will react. DS was terrified of the characters

. He loved them from a distance, but freaked out if they got too close. He had no issues with characters on our last trip when he was 9 mos old, but he definitely had issues with them this time!
Have fun!