You should be very careful with this. Even a relatively low TTL of 300 (5 minutes) can be too long to wait during a major outage. Make sure changing CNAMEs is a very rare thing, and be prepared to tolerate inconsistency.
It's also worth noting that some widely-used pieces of software cache DNS lookups in-process (MongoDB), so changing a DNS name is no guarantee that all connected processes will automatically fail-over to the new machine unless restarted.
It's also worth noting that some widely-used pieces of software cache DNS lookups in-process (MongoDB), so changing a DNS name is no guarantee that all connected processes will automatically fail-over to the new machine unless restarted.
Moral of the story: distributed systems is hard