I would go with 4 interfaces (3 NICs)…two WANs, one LAN, one VLAN. Disable the internal DHCP on the APs. Use the DHCP from pfSense for BOTH VLAN and LAN, install captive portal and enable it on the VLAN. Make sure that the two interfaces are on disjoint subnets, you can also set the default rule on both interfaces to prevent traffic from going from VLAN-LAN and vice versa. LAN becomes VLAN1 (the default VLAN) in a setup like this.
We only have one WAN here, but use the same VLAN for wireless setup. If your APs can support it, setup two SSIDs; one on the LAN for your employees to connect to the Citrix servers, and a second on the VLAN for guests to hit the captive portal for web access.
The full setup would be like this: WAN1/WAN2 (NIC1/NIC2)-> LAN(VLAN1, NIC3, 10.1.1.1) or guest VLAN (VLAN2, NIC3, 192.168.1.1)