Etiquette wise I want to know if this itiming is fair to our guests

We are having our ceremony/reception at the same venue. Ceremony will be in a separate room and after the ceremony they can all go into the large reception hall.
Ceremony will start on a Friday at 5:30 pm (done by a minister) so I expect everything will probably take 25 minutes at the most...(we are not expecting alot to attend the ceremony or cocktail hour because we are doing things on a Friday night, but we are still planning for it just in case they do)
from 6 pm-7 pm will be cocktail hour that will also be serving appetizers (around 4 different kinds)
(During this time we will be taking pictures)
We plan to arrive back between 7 pm-7:30 pm....I am hoping for closer to 7 pm as we don't plan to travel further that 10 minutes from the venue. I just found out that the venue has a pond on location that we can take pictures at, but I still have to look at it to see if its feasible (not too far to walk to, has anything odd in the backround, etc).
**We are also taking pictures before the ceremony with my bridesmaids/groom with his groomsmen** So that we can focus on family/whole bridal party pictures during that hour.
Hall manager is insisting that the dinner be served right at 7 pm which I wanted a little leeway in case things run behind, but she's suggesting the guests will not be happy....I just didn't know if the 7 pm time frame was feasible for all of us to be back by, plus make our entrance, and we wanted to do our first dance before dinner is served (which is buffet style).....I would be thankful for any constructive help with this

Thanks ladies!