Praise God that you have so many children! We're not at that point ourselves, but personally I would go for more workshops if you have the teachers to accomodate that. I find that a nice sized class is no more than 10, especially if they are rowdy boys
. A smaller group encourages more sharing as well.
We have had three groups - age 4 to grade 2, grade 3 and 4 and grade 5,6,7. Since the fall our numbers have been down and so we split into two groups. Younger and older. That worked well because too small of a class doesn't have good dynamics either. Especially for games and drama. Today I had 14 kids in the older group. Whew! If that keeps up I will go back to the three groups.
Hope some of this helps you.