As Disneyland is an older park (very much pre-ADA) most of the attractions are not mainstreamed and there are alternate entrances for wheelchairs. When you get to an attraction either look for a sign or ask the first CM who appears to be controlling the line.
At Disney California Adventure all lines are mainstreamed, so you will just use the same queue as eerybody else.
If he is not in an obvious wheelchair, you can ask, at Guest Relations, for a GAC which will allow you to use a stroller as a wheelchair. The GAC rules at DLR are the same as at WDW.
As far as restaurants, it has been a while since I have been to DLR, but I can only think of three sit-down restaurants in DL, the Blue Bayou, the Plaza, and the Carnation shop. However, unlike WDW, Downtown Disney is right outside the entrance to DL so there are quite a few places to eat there.