Hi @BobMac - just a few things to consider here.
For DHCP handling, you would configure DHCP relays or DHCP servers on the Switch -> Routing & DHCP page in Dashboard. Keep in mind that both DHCP & L3 routing are configured on the switch stack, not the individual switches. You can see the stack setup & status on the Switch -> Switch stacks page. The default route would also be configured on this page at the bottom under "Static routes".
Meraki does not have a global VLAN definition like Cisco or other switches. If you configure a VLAN on any port on a switch (or any port in a stack), that VLAN is now in the list for the entire stack.
If ports on the second switch are missing the WiFi VLAN's, you can just edit the ports with AP's attached to the correct config. Meraki switches do use the same access/trunk setup as Cisco switches.
MRCUR | CMNO #12