I personally would let them be but that may just be the wildlife biologist in me talking...

That aside, I would expect them to adapt very well to captivit. I've never heard of problems getting toads to accept new foods and considering that you already feed them I can't immagine these toads will be an exception. Alternatively though, the toads did learn to come to your place for food -- there is no reason that they won't also learn not to continue doing so after you've left. It's hard to tell how the new owners will react to the toads but I don't think it is likely that they will see them nearly as often as you do after a few weeks unless they start feeding them as well...