I do just what you described...everyone at the kitchen table and the little ones are in booster seats. The key is having all the paint/paint trays, glue etc or crayons or markers out and ready to go along with everyone having a paper with their name on it. I go right from morning snack to clearing the table, getting the smocks on and handing out the art supplies. Kids are not going to sit patiently for you to fill paint trays or tear off paper for each kid. They want all their stuff at the same time as the kid next to them so you have to be prepared and move at ultra speed.

I try and get the art stuff ready during a quick free play session and before morning snack and then do morning snack and transition to craft/art time

why not give the little kids the big fat Crayola crayons and some construction paper or a paper plate with a little dab of paint so they can fingerpaint?

The hard thing about craft time is that some kids are way more competent to handle materials and to have the required attention span but usually everyone can do something to varying degrees.

Art time can be uber messy and stressful for the provider but the kids love it