I guess it depends on the child's age, but I was just at Swiss Chalet, which is pretty kid-friendly.  I fed my 10-month old parts of my chicken (without the super salty dipping sauce), whole wheat bread roll and baked potato, along with other food that I had packed with me (some fruit, formula).  They have high chairs too. 

I know some moms bring a jar of baby food (entree-type, like 'Beef Stroganoff') to open wherever they happen to be when it's lunch time.  Also, on longer outings (like the zoo, or hiking), I've brought warmed pasta sauce and quiche in small baby Thermos, which keeps warm for a few hours.