Don't suppose DNS entries resolve to loopback IP addresses do they?
One way to change en masse: Database manager --> Nodes (View) table --> Enable table editing -> check DynamicIP box
You could also do an 'update set' SQL command.
Warning--mistakes in database can be "resume generating events", so always good to have a backup.Here is an example (although different use case) that should give you some idea what is involved although no special query is really needed as was done in step 4: Change the location of a node in ICMP polling method - SolarWinds Worldwide, LLC. Help and Support
Are you changing polling method as well to ICMP? obviously needs considering and maybe testing one first to see if it works.
you could try an update to the IP address through SQL similar to this:
You could create a spreadsheet with the old and new IP to populate it if you're not proficient with SQL