bootp helper secondary

Currently I have the following setup which works great across a EX2200, EX3200 or EX4200 running 12.3R6 to 12.3R11 depending on the site.  

set forwarding-options helpers bootp server 10.10.10.1

set forwarding-options helpers bootp interface vlan.10

set forwarding-options helpers bootp interface vlan.20
set forwarding-options helpers bootp interface vlan.50

My problem:

I need to add another vlan.100 but it will go to a different dhcp server (10.10.100.1)

Is that possible with bootp or do I need to learn the new dhcp-relay options?  

It will become a guest network so it may run in a different router instance depending on how the design works out.

Any suggestions?

Thanks,

Todd