Multi-Instance Failover Cluster SQL Cluster
Points to note:


A 3 node cluster requires SQL Server Enterprise Edition. You can deploy a 2 node cluster using Standard Edition.
If you are placing an active instance on each node, then each node will need to be licensed. That is 4 cores per node as a minimum so at least 12 SQL Server Enterprise Edition core licenses, possibly more if your load requires it.
You need to thoroughly test performance with all instances running on one node. If you lose two nodes and all instances fail over to a single node, can your hardware cope with the load?