Well, Hoop de Doo isn't a 'sit quietly and watch' show, it's pretty boisterous, and might hold his attention.
I don't know if you meant "dinner AND entertainment"....if so, La Nouba is not a dinner show, it's a theater show. No food served, though there are lots of good dining options in Downtown Disney. I found La Nouba to be very, very loud, so it might not work out for you, but it is very entertaining. There's lots going on all the time, and also might hold his attention.
Another option would be Whispering Canyon Cafe at the Wilderness Lodge. It's not a show, but it's a western-themed restaurant where there's always all sorts of mayhem going on - stick pony races, people singing. An antsy 3-year-old wouldn't even be noticed there.
You might also consider the Rainforest Cafe and T-Rex restaurants in DTD. There's no actual show there either, but lots of animatronic animals and various effects - thunder storms, meteor showers, that kind of thing. If he does get restless, someone can get up and walk him around the restaurant to look at all of the scenery and animatronic critters from time to time.