Advertise Pi-hole IPV6 as DNS

Hi All
Is there any way that i can advertise an IPV6 address as a DNS server, i am using HE 6to4 tunnel but would like my clients to use my local pi-hole via IPV6 as resolver, pi-hole then points to the router and then OpenDNS. I have this working ok with IPV4, but of course the router is supplying the DHCP and I use dhcp-option=6 to set pi-hole as DNS server there.

I am completely stumped with the IPV6 DNS though.....any help would be greatly appreciated