i have HAproxy & Keepalived currently. Using the DO featured floating IP only helps with 2 stacks in the same datacenter. Cloudflare Doesn't automatically failover, half of users will be without service if i use several DO featured floating ip's.
If you're looking to route traffic based on Geolocation then something like this might be helpful in front of your stacks. Since DO IPs are tied to a single physical location and cannot be multicast or otherwise refer to more than one location you would either need to have a single entry point (which could be a floating IP with failover handled by something like heartbeat), use a service like CloudFlare (which could be put in front of the failover / heartbeat / floating ip configuration), or use something like geoDNS to route traffic to the closest data-center, implementing failover in each DC individually.