Reception Dinner

I think if you need room for decor & dancing, you should ask the restaurant if there is a room available for you to do so!
Also, a LOT of places have started doing micro wedding packages. Maybe see if there's places in your area that can accommodate, so you can get everything you want! Just food for thought!

I think you need to have a phone conversation with the manager or whomever takes reservations to determine what the restaurant will allow. Have you list of questions ready to go.

Most restaurants (if they are not usually wedding reception venues) most likely will not have space for dancing unless you rent out the entire restaurant and they move tables, chairs, etc. If you are in the main dining area, then it would be inconvenient for the diners who are also there trying to enjoy their dinner. Some restaurants also don't allow decorations or at least they don't allow a specific way to hang or attach decor

Length of the photographer is going to be dependent on how the restaurant operates, and what you can do. It sounds like they will be there for a little bit to take some photos, but then the rest may just be you eating.

Step 1. Talk to the restaurant and have 1 point of contact. This will help the this person said this and that person said that. Once you get all of your questions answered and have a plan, then you can determine how long the photographer needs to be there.

Agree with the other comments: Call or email the events coordinator ASAP. Don't worry about bothering them, this is their job!