We use a storage box too or our bigger girl (3.5) and or our little man (18 months) we found the best thing to use, as he wasn't quite old enough (at 1) to sit on a chair at a table, and I was fed up with him on my lap (squealing whenever I dared to shovel something into my mouth and not his!). Probably too small for your young one, it was a little plastic seat designed to be a booster on a normal chair, it had a backrest and a tray that swung out to let him loose and clipped in front of him at meals times and other times you didn't want him wandering around. It was easy clean and he loved sitting in it. He'd take himself over to it and sit in it for ages. It helped keep him away from the campfire while keeping him with everyone and the action.
Not sure on the brand as we bought it off ebay but it was a brightly coloured plastic booster seat.