It doesn't sound like my idea of a good time, but I can understand *some* of it. I have hosted a party on my driveway/garage before b/c I don't have a large house and live in a condo so I don't have a yard per se. However, it was a family party and everyone could go inside if they wanted to, and we have a few chairs. I can honestly say we don't have a ton of chairs, but we try to borrow some when we have events (not frequent) at our house. I do think it is pretty bad form for the birthday boy's father to occupy the seat the entire time if seating was that limited.
When I go with my children to birthday parties I don't expect the host to provide drinks/food for me. With that said, I have never been to a party where the host hasn't at least offered water.
Beer? Well it isn't my thing at a children's party but I guess I can't fault another family for offering it. I generally think this is more appropriate at family gatherings or events with close friends only. It does seem a little odd at a party with classmates where many of the adults there are acquaintances at best.
Hopefully your child isn't best friends with the birthday boy so you wont have to deal with too many playdates!
All in all this does not sound like a party I would enjoy, but I guess it will make for a good story. :)