D.S.
Have you checked to see what the yurt provides? The one we stay at (in a KS state park) has beds so we need pillows/sheets/blankets but can get away with not having sleeping bags unless we need them for warmth. You can also find out if the yurt has electricity or heat in case it is cold there.
Snacks and meals might depend on what kind of cooking you will have. Just the campfire or do you have a camp stove, too? A camp stove makes a big difference if you want to heat tea/coffee/cocoa, soup, basically smaller amounts of any liquids.
How long will you be? We do a lot of packet cooking - veggies, potatoes, etc. prepped in foil packs before we leave and tossed into either the fire itself or the grill above when needed. If longer than 24 hours and the weather is warmer, you'll need to replenish the ice in the cooler for any perishables you might bring for the other days.
I would say definitely bring your chairs, firewood, toilet paper, trash bags, fire starter material, matches, the items you need to cook with and eat with, games to play with the family, warm socks, and whatever munchies you like!
Have a great time!