Dinner near the River Rink?
If it's early enough (6ish) Continental is very close and would be ok. Turns too much into a lounge later. Check the menu first to see if your kid will eat the food--there is no children's menu.
A little further, DiNardo's Seafood at 4th & Race is family friendly but probably a bit too far to walk. The food is ok, don't order anything too ambitious.
Whatever you do, you should consider Franklin Fountain for ice cream afterward.