5.2! - going back a few years here
Normally, cluster services are not started by default. Why reboot, restart cluster services, have the application return - only to crash again.
So, initially, I would go to a working node - that currently holds the resource group, and set it so the it does not return to "primary" node when that node goes online. Sorry, I have forgotten the term used in 5.2 days.
Or, you just run
# smitty clstart when things are not too busy because there is a good chance that the cluster will stop one or more resource groups - assume at least one - and try to reactivate on the reactivated node.
The less drastic measure, compared to what you suggest, would be to remove the resource group from the cluster configuration. Just "force" synchronize to all remaining nodes.
P.S. make a snapshot - ALWAYS - before making any changes to any unknown configuration.
so - basically, the normal idea would be to clstart the inactive node(s) and let HACMP do its thing. This assumes the configuration is ok to begin with.