The best purchase that I ever made for my daycare was a white noise machine! Wow! What a difference. I bought mine at Superstore - made by Conair $24.99. I use the "white noise" setting and put the kiddos down for naptime and don't hear a thing! I actually bought 5 of them haha! I have a babbler, and a banshee screamer. I also put the noisiest one in the furthest away bedroom of my house, the good sleepers all sleep in the same room.
While I agree with the others about getting up after an hour, honestly an hour is not a long enough break in my opinion. I know for me, it takes me nearly an hour to clean up and eat my lunch. I think you should keep them napping for 2 hours. Good luck to you!