Yes, the owner should provide ALL food, meds, leashes/harnesses, etc. Other things you (toys, treats, etc.) can decide upon. I message the owner one day before to remind them of what to bring. When we have our M&G, I give them a dog info sheet, which has all the important info/contacts/ behavioral stuff) and they return it to me when they drop off their dog.
Excellent that you obtained dropoff and pickup times before the sit started. Way to go! OK, now you can modify the booking request to reflect the extra time. Tell the client that each "night" of boarding is only good for up to 24 hours. So if they drop off a dog at 8 am, then they have to pick up the dog by 8 am on the last day. Nobody has ever quibbled about this, when I've explained. You can either add another day onto boarding or just charge your daycare rate. Oftentimes, I just tell the people to drop their dog off the night before, so they don't have rush around in the a.m. when they're going out of town. It all works out perfectly since they're going to pick up the pup in the evening as well and I don't have a daycare rate, but you do.
You are off to a good start. Good luck and just go with your best business sense.