It's difficult to be a server at a large ballroom, catering to over 250 guest at 1 time, but doing it while trying not to trip over cords, slip on grass, or work in an tented kitchen with generators and gas tanks was definitely not easy. However, many guests came up to me to give the staff many accolades and the bride and groom seemed to be having the time of their lives (take goodness I had my emergency suitcase with me; the groom needed advil to get rid of his headache after the ceremony).
Eventricities was the production company that designed the wedding reception, but I'm not sure which tent company they used. However, here are some Philadelphia-local tent companies...
This website has a great tool to design your tables. They offer tents, in addition to linens, silverware, stemware, and china - anything and everything you may need to design your reception.
Another place is Celebration Rentals/Event Quip.
Just to give you an idea on how many servers and bartenders you should have for your occasion in a tent:
Last weekend's wedding : 250 people: 25 tables - 7 servers - 4 bartenders - 4 bussers - 1 maitre d
For our wedding: 12 tables and 6 servers - 1 bartender
1) weather : tent holds in the rain and wet ground should not be a problem if you have the tent up a few days before the reception.