18 month old refuses high chair and booster seat
Is it the confinement he doesn't like? Perhaps you could just build up a chair so he was higher. When I was little folks just used to use a big phone book or dictionary to prop kids up higher for a while. I do think my kids stopped using special seats around that age. It is a very wiggly time of life with lots of attention shifts. Perhaps try it without for awhile. He should settle down over time. If he gets up too often, perhaps you could set a time limit on the meal so he simmers down to focus for a bit?
Youngest either sits on her butt or knees and does great.
My kids also like meal times. My husband also eats quickly and is usually finished first!
My kids never liked high chairs or boosters once they were actually eating (as a baby my older one would sit in one, but he didn't really eat until 15 months or so). We had all of our at-home meals in the living room with dh and I on the couch and children's plates on the coffee table with them eating if they wanted, playing, or whatever. Getting them to sit through a meal has never been high up on my list of to do's but now at 8 1/2 and 3 1/2 they usually seem fine to me at restaurants (my older one always was great in restaurants, little one has usually been a terror but better lately).
Have you introduced play dough or fingerpaint yet? Those are GREAT for special high chair/booster fun. The condition of playing with either in our house is sitting in the high chair at the table (we have one of those high chair/chairs that just pulls up to the table w/ a seat that adjusts to DS's height as he grows--if he stands we snap him in with the buckle, so he's pretty good about staying seated)
My 18-month-old is the same way. At home, we have a "high chair" that straps to a normal chair- I've taken the tray off and don't strap him in, so it feels more like a normal chair, while still giving better support and containment than a kitchen chair. At restaurants, we sometimes try a high chair, sometimes a booster, sometimes neither. I'm just very consistent with telling him "On your bottom." when he tries to stand up. He usually ends up on my lap eating or nursing more than half the meal. Booths are nice for allowing some wiggle room and containment without the fear of falling off a chair.
It may very well be a phase. DS rejected the highchair/booster seat right around 17 months. We bought him a little table and chair to eat at for a little while. Then he wanted to eat at the table with us. At that age we focused on the things that were safety issues (standing up on the chair, trying to climb on the table, etc.) and worried less about manners. If I had a dime for every time we said, "on your bottom please" I could buy a new car! He'll be 2 in a few weeks and he doesn't really stand up in his chair anymore and he does a pretty good job of staying at the table during mealtimes. He does still get distracted (toys! kitty!) but we're working on the concept that if you get up from the table, that means you're all done and mumma is going to take your plate away.
Mealtimes and dinners out are just tough at that age! It does get better.
What about a tall chair like this:
It might let him feel like he's sitting in a regular chair, but it is of a height with the table so he maybe won't be as tempted to stand up. I imagine it would work for any kid up through the preschool years, so it would still be of use for some time.