I believe that it is an ok idea. Whether it is a "good" idea depends on what alternatives you compare it to and what criteria are important to you. You can run DHCP on the router and perhaps avoid the need to have an additional piece of equipment in the network. Perhaps that makes it a good idea. Running DHCP on the router will make the router more busy and consume some additional memory. If that impacts performance it makes it a less good idea. If you want to track DHCP utilization more DHCP servers probably have better reporting mechanisms that the router does for DHCP.

You know your environment and your requirements much better than we do. Since we do not know what kind of router it is, and do not know what other kind of load you may ask it to handle, we are not in a good position to say "good" idea or not.

HTH

Rick