It's a wonderful service you're going to be doing. I don't know a thing about treadle sewing machines except that you'll probably wind up with legs in great shape. I have just found out that wallpaper scissors are long term the
best you can buy, and they can be purchased in a hardware store for between $8 and $10 each. They cut fabric
as well as paper. Connecting Threads has thread that is sold at a very reasonable price. They're big spools, and you can get them in sets also for $10 or $11 that include approximately five or six spools.
As far as the sewing machines, I would suggest calling a manufacturer and see if they have anything they could
send you. The machines are, I'm assuming, standard sewing machines. The only difference is the treadle, which probably will need some oiling. Try Overstock.com for some of your supplies. Also, I see you are in Alaska. Connecting Threads is located either in Oregon or Washington. I wish you all the best. There is someone you can ask for help whenever you need it, and the next thing you'll know the answer is right in front of you.