using the new DHCP services is not mandatory.
Using the bootp like you does, there is no need to change to the new dhcp services.
Configuration of IPv4 BOOTP/DHCP Relay using new services describes really good the new DHCp services and there need or not.
For youre use case, snip from the document:
"For backwards compatibility, the legacy DHCP (BOOTP/DHCP) services can still be used with newer Security Gateways and Security Management Servers."
The new DHCP services allows an improved configuration of the rules for DHCP relay.