TX needs PHL recs for casual dinner for 16-HELP !
citysearch.com is good for searching for restaurants and they will give you a good for groups option.
my recommendations include....
the independence brew pub (1150 filbert street) next to the reading terminal. is very good for groups and they have alot of space. is about a 4 block walk from the hotel.
maggiano's little italy (1201 filbert) is a half block from the brew pub and is also good for groups if you reserve in advance. the advantage of these two is that they are near the reading terminal which is also a great place to eat if people want to break off from the group and is very close to your hotel (and is one of my favie places in my hometown).
there is a buca di beppo in town too if your taste buds can handle it. i personally hate this chain, but many people like it.
los catrinas on 16th and locust is awesome (5 block walk), but i am not sure how many big groups you have. they might not be able to accomodate you. and that's all i have that's close to you.