Name servers can be fairly complicated and it sounds like you are starting at square one.

Since you only have 5 sites, you might want to let someone else manage your dns stuff. Then you only need one ip for all your sites. Your hosting company likely offers dns services free with your server.

Rather than trying to run 2 named daemons on your hosting server you would be better off letting someone else add the dns records to their dedicated name servers.

It is nice to be able to mange dns records. But with 1 ip, you wont need to make too many changes.