We are pop drinkers at home (oh, the shame) and have company often enough I don't mind keeping extra in the garage. I usually buy cans because cans on sale are cheaper than 2-liters that someone drinks 1 glass of, then you have to pour down the drain because it goes flat. I think I grabbed a 24-pack of coke and diet coke and a 12-pack of root beer and sprite for DD's party, a case of bottled water, and juice boxes. I assume there was plenty, because there were leftovers of everything.
One of my nephews can't eat dairy, so I usually have cookies or something he can eat in addition to cake. Other than something like that, I wouldn't bother. (And if it were an adult I probably wouldn't worry about it but I feel bad leaving kids out.)
I got juice boxes, milk (horizon - small likee a juice box) and small waters for the kids (ages 1-7).
We did pizza so I assumed 2 slice per adult, 1 per child and then rounded up. I also had salad and pasta with marina sauce. The party was earlier so I figured adults would eat on the lighter side and they did.
ETA - for some reason I thought you asked about food too - sorry. For about 20 adults we had soda (bought 6 bottles, had 2 unopened), iced tea (1 gallon that didnt get finished) and water (24 pack with lots leftover). I had cookies as favors but the only dessert was cupcakes.
I usually do 2 liters, water, iced tea, Capri sun, then Make a pot of coffee after the meal. With the soda I just buy a few flavors- coke, diet something, and something caffeine free. We would use anything opened for mixers later.
We usually grab a couple of 12pks of different flavored sodas and put them on ice along with a case of water. I get some juice pouches and milk boxes for the kids. I wouldn't think you need another dessert, but I usually put out another sweet item even if it's just a fruit dip so people have options.
Oh and coffee with disposable cups with lids. Our guests tend to be big coffee drinkers and like it with cake so we go through a couple pots during the party.
I've done coffee, water, and punch for birthday parties. I love pop, but punch was easier. I would probably pick up several 2 liters. My job used to entail lots of meeting planning, and groups of 20 would go thorough about 6 2 liters in 3-4 hours.
You don't need another dessert, but feel free to add more if that's your think. I love to bake, so I had a few different options.
We don't serve soda just water bottles. For DD2's last bday she really wanted juice boxes so I bought organic apple juice boxes which is what they had served at the other parties from her class.
I would do about 10 2 liters of different kinds - regular, diet, and flavored (like dr pepper or mt dew). We'd drink anything that was extra so no issue on that. I would also have bottled water. I would be fine drinking water but would rather have pop then just water and lemonade.
I'm not a cake fan so would enjoy cookies. Or even something like rice krispie treats? For my twins baptism I didn't do cake. My mom and I made frosted cookies in the shape of a cross and mini cherry cheesecakes. I plan to do cookies for their 1st birthday party too.
We usually grab a couple of 12pks of different flavored sodas and put them on ice along with a case of water. I get some juice pouches and milk boxes for the kids. I wouldn't think you need another dessert, but I usually put out another sweet item even if it's just a fruit dip so people have options.
Ditto all of this (minus the milk boxes, which didn't occur to me). I would probably just do cake and fruit for dessert - although in the interest of full disclosure, I also served brown butter Rice Krispie treats at DD's last party, but that was because I wanted some for myself