You can buy the heat packs that are normally used for shipping ball pythons, put one in a sock and place it in each snake's cage or tub.

Heat Packs
http://superiorenterprise.com/store/...d=33&Itemid=53

Or you could get a back up power supply to keep running your heating; this would probably be best to get you through a short power outage without having to do anything.

http://www.apcc.com/products/family/index.cfm?id=22

Heat packs are not as good as having your equipment running but they will get the job done if necessary.