Most probably your core switch has the gateway ip of the subnet like 192.168.1.1. If you want to enable ip-helper on your access switches, then you need to assign ip to the vlan on access switches something like from 192.168.1.2 to 192.168.1.6.
In this case all 6 switches will translate broadcast DHCP discover to unicast and send to DHCP server. DHCP server will receive 6 Discover and reply with 6 Offer. These 6 DHCP Offer will be relayed by all switches to the host so host PC will receive 6 offer. This means a lot of process for everyone without a benefit.
DHCP relay is not something cause high cpu load. It is always best practice to enable ip-helper where your gateway ip is configured for the subnet.