@Gwendolyn33
I'm in Australia so I don't know the Virginia area at all.
However I would think the best starting point would be to search for reservations that can accommodate large numbers of people - you enter the number of guests when you are searching.
I just had a quick try - I wasn't able to enter more than 10 children all up ( 5 children, 5 infants) and 16 adults - not quite the way your group is composed but the right totals.
I got 93 hits for Virginia for the dates you are after.
I would check through these - find places that meet your costs expectations and contact the host regarding the dynamics of your group...