This is NOT a good option, but better than the sick option.
Heat tape runs at a given temp without a thermostat. Take two sticks and put them under each tub to raise the tubs several inches off of the heat tape.
Make sure to get their warm end around 90-92 and the rest should be ok until your thermostat comes in.
No heat is worse than the alternative.
In the future, never get a pet unless you are fully prepared ahead of time.
Fish don't come home unless your fish tank is set up and running.
Rodents don't come home unless you have a cage for them.
Snakes don't come home unless you have their set ups fully functioning before they are shipped.