Good evening Tony,
Congratulations first on your big day coming up. Lots to prepare for and it sounds like you have in terms of organizing a small wedding.
Never like to think what could go wrong on a wedding day as this should be the most wonderful time in your life. Thinking though of what could go wrong includes what you stated above (late arriving guests and professionals taking care of things such as flowers and food). How to prepare is important just in case these things happen. Start with having someone you can trust in your wedding party to be in constant contact with the florist as well as any musical group and food service to be sure all are on-time and know where to go. You have too much to prepare for and having someone you can trust do the work ahead of time will cause little to no disruption to the events that day.
Great that you are having reception at a local restaurant that a friend is offering their services. Buying the alcohol in bulk is a smart idea as the restaurant pricing will be much higher than doing the purchasing yourself. Check this calculator to get an idea of the cost involved:
Look at places such as Costco for example that you can purchase in bulk at the lowest cost available.
As for the flowers, again great idea as a freelance florist can do the work for much less than a more expensive one can. Work within a budget and stick to that as the florist should be able to offer suggestions on flowers that are lower in price in the summer season.
Best to you for the wedding as it sounds like everything is ready to go and without any problems.
I hope that this information was found useful as please inform me of any additional questions/concerns you have. Also if you could take a second to rate my assistance so that I know my help was found useful today.