On 7-mode systems all the LUNs composing a dynamic disk had to be on the same storage controller.
ONTAP 9 and Clustered Data ONTAP do not have this requirement unless PRs (persistent reservations) are required. If that is the case, all the LUNs should reside on the same node.
So if your environment does not need PRs, you should be ok moving the volumes/LUNs... just pay attention to what Marcus said.
Have iSCSI multipath correctly setup, SLM, etc..