Is it safe to have feral cats sleep on deck?

I put my dog's old bed out on the deck for the feral cats that eat on my neighbor's deck (the decks are basically touching one another and cats constantly cross over). It's pretty cold out and so I wanted to give them a warm bed to sleep on. I've never dealt with feral cats but there are so many in this neighborhood and so I feel for them sometimes. My concern is if this is a bad idea from the standpoint of my pet dog who goes out on the deck everyday. Is there anything to worry about with the bed? My dog goes to sniff on it everytime she goes out (she is so interested in cats). I sprayed the bed with flea and tick spray for indoor use. Is there anything else I should worry about or should it be ok? The two or so cats that use it look so comfy in it. It is out in the open so it does get wet but the cats use it as soon as it dries out. I don't want to take it away, but if it is not a good idea I'd like to know. Thanks!