I like superfun's idea..that is really creative and space saving!
I have this table from IKEA http://www.ikea.com/ca/en/catalog/products/40104294/# with these chairs from IKEA http://www.ikea.com/ca/en/catalog/products/90267556/ I love it and it's small enough to not take up much room but also big enough for 6 children to sit comfortably at.
As for ages, I am limited to 2 under 2 years and no more than 4 in total. Typically, I usually have a young crew though.