I use RB450s with epmp all the time in this scenereo. If it's a single AP I just add a /30 to the interface facing the ePmp for management and set up another IP for the customer gateway. If you are using a ring just make it a /29 or /28.... No VLAN configuration needed.
Are you saying you want to hand out DHCP to both the radios and the client routers, on different VLANs?
If so, enabling Management VLAN on the radio and setting up a DHCP server on a matching VLAN interface on the Mikrotik issuing DHCP should be all you'd need.
I'm assuming you know what to do on the Mikrotik end, since you've already done this with PMP450. On the ePMP radio end just enable Management VLAN in the Network settings, assign your VLAN ID, and give it a priority if you want, and enable DHCP.