Any suggestions on working up to eating at a restaurant?

I want my 11 year old autistic son to be able to eat at a restaurant. We started going to a café and sitting outside. We've moved up to sitting inside now and I don't know where to go next. Now we go into the café we have a routine (he says hi to the owner, we sit at the same table, eat the same food, etc) so he's okay doing it, but when we first arrived, it wasn't fine. Problems are with: getting him to sit in a chair, be relatively quiet, and eat something. If it's noisy or crowded, he'll struggle more (the café is usually empty). Is there a particular restaurant that's really family -friendly? Any suggestions at all?