What is the possessive for several names?
"Alice and Bob's houses" implies that Alice and Bob jointly own more than one house. "Alice's and Bob's houses" could also imply the same thing. However, it would more commonly be taken to mean "Alice's house[s] and Bob's house[s]". To remove all ambiguity and still retain a similar form to what you now have, I would suggest "Alice's house and Bob's house".