I always have them meet me at the processors and let them pay. Getting reimbursed could always turn into a problem that could cost you more then money
Do you have a seller permit (license to sell in your state)? Will you collect sales tax (State/County/Stadium)? Will you submit that tax? Do you have liability insurance incase your "friends" get sick/choke/get lead poisoning and they sue you? I can go on if you like..... IMO tell them if they want venison go hunting or buy their meat from a license deer farm. There are several online sources.
Good idea to post your intentions on the internet. Game department personal NEVER troll these sites looking for potential violators.......NEVER.