I was looking for the pictures I took of the tables at Crystal Palace so I could post one. Here it is:
We were at a round table for 8 and had no problem getting DD's wheelchair pulled up to the table. She needs at least 27.5 inches of clearance for her armrests to fit under the table and that was no problem.
In addition to the type of table shown here, they also have rectangular tables the are against walls. Those have a bench seat along the back, closest to the wall and the same kind of chairs on the side of the table that is toward the room.
At Crystal Palace, my DD's wheelchair armrests fit under the table easily. Her armrest needs 27.5 inches to fit under. I didn't have a tape measure with me, but estimated the bottom of the table to be about 1 inch above her armrest (so, it's about 28.5 inches).
How high of a table do you need?