Dynamic IPv6 prefix from ISP, prefix delegation from firewall to layer 3 core switch (Cisco 3750G)

First of all, I'd like to say that this is a homelab environment, hence the outdated switch. I'd usually not ask questions regarding my homelab in this subreddit, but no other subreddit could properly answer me and the gear used is enterprise grade.

My ISP supplies a 56 bit prefix, allowing me to create 256 subnets.

Vlans and intervlan routing is all done on the layer 3 switch (3750g), which is currently IPv4 only. This switch is connected to a pfSense box via a layer 3 interface on the switch.

Now what I'd like to do is to delegate a slice of the 56 bit prefix, to the layer 3 switch, which is where the vlans are configured.

I've thought of one way to do this and would like to know if this is possible, or if there are better ways.

A DHCPv6 server on the firewall, which the layer 3 switch is connected to. Automatically configure the layer 3 interface on the switch with an IPv6 address and run a dhcpv6 client to obtain a slice of the 56 bit prefix (58 or 60 for example). This prefix would be used on the SVI's, combined with a prefix ID. This way, if my ISP supplies a new prefix, everything else will dynamically update.

Thanks in advance.