The DHCP Settings page of the web GUI provides the ability to input the 'Router (gateway) IP address' to be used in a dhcp-option=3 (or dhcp-option=option:router) entry that will pass the address of the internet gateway router to dhcp clients.
It would be useful to have a similar mechanism to allow the administrator to provide the 'NTP Server IP address' to be used in a dhcp-option=42 (or dhcp-option=option:ntp-server) entry that would pass along the address(es) of preferred NTP servers to the dhcp clients.
This request may be what was intended by an earlier feature request I found:
NTP Pointer in DHCP Server