We have the same issue with our son who is 26 months. He is just so busy doing other things he won't take time out to eat.
One solution is to offer him food only when he is REALLY hungry. I'm not saying to withold or anything just don't have him sit with you at dinner time unless you know he's ready to eat. My little boy eats soo much better when I wait until he says "eat, eat" and goes to his chair before I start making his dinner. If he is really hungry he sits, he eats and then it's over, no mess and no battles.
For a while I felt that family dinner time was important, that we all needed to sit down together to establish a routine, but this simply goes out the window at this stage because it turns into more stress and crying and battling then it's worth. Not only is HE not eating but then I don't get to eat because I am constantly getting up to pick up his cup he drops or food he is throwing etc. If you want to sit him down with you make a rule that he can eat while he's sitting but when he gets up he can't have any more. Take his plate and refridgerate it until he shows some interest in food later. When he is hungry later just reheat his left overs. Be careful though, he can turn this into a game. If he gets down I would suggest making him wait at least a half hour before reseating him otherwise you could get stuck playing up and down, up and down.
Also, be careful not to give him other snacks or alternatives when he doesn't eat. My son would sometimes not eat what I make him so that he could have yogurt or cereal later. I finally caught on and ended that, thus the left overs reheated.
As far as restaurants go, we usually opt out of dining out with him as its far more stress than enjoyment. If you find yourself stuck in a situation when you have to go out, keep a small back pack in the car with restaurant friendly toys. We use Mr. Potato Head, a small magna doodle, some hotwheels and some little Mickey Mouse Club House figures and Play Doh. He ONLY gets these toys at restaurants so they keep his interest through the meal.
Hang in there this is tough, but this too shall pass. And he's growing like a weed despite his picky and unruly eating routine right now!