here's what I think:
3:00-3:30 PM Ceremony
3:30 - 4:30 PM Cocktail hour
4:30 -(whenever they tell you have to leave) reception. You could do all the formal stuff, first dance, cake cutting speakes and then ask for dinner to be served around 5:30 ish. Then dancing and fun the rest of the night!!!
Also, if you are worried about the photographer contact them and see how much it would be to add a few additional hours.
Hope this helps!
Meagan