Hang on, so you're doing your actual wedding ceremony and your reception in three hours? Surely you will have to take photo's after the ceremony otherwise you wont have any photo's once your are married?
When the room is being set up for the reception where will the guests go to relax? Or will group photo's be taken during this time?
A few things.
1. Does the three hours include time to decorate the room for your ceremony, or will the venue do that for you beforehand? Do the three hours also include removing all items from the venue?
2. I would say guests/the groom need to be in the venue at least 15 minutes before the actual service to give time for everyone to be seated, that is fifteen minutes gone, then the actually ceremony, weddings I have been to tend to last 30 minutes.
So with seating guests, the ceremony if its the same time of every service I have been to and getting the room ready for the reception that is almost an hour gone, leaving two hours for your reception.
So, everyone enters the reception where you and your husband greet everyone and your bridal/groom party if you have one, maybe five minutes (its a good idea to have a board with the seating plan on, its easier for the quests). Then its probably best to do speeches first as they are the most important thing so you don't want to run out of time for that and cutting the cake, that could introduce the first dance, after that you could do the flower toss.
Have you thought about asking if a family member/friend would pay for an extra hour instead of buying a wedding present?