Replacing AirPort Extreme: Seeking advice

Hi,

My wife and I own a smaill campground (110 RV sites). We get broadband from the local cable company at 100 Mbps via their modem. Our AirPort Extreme acts as the controller for an Office LAN. It consists of a few wired PCs and printers and a couple NanoStation M2 APs for staff phones and tables. In addition, we offer guest wifi with a Checkbox Systems setup connected to the AirPort Extreme. I want to replace the AE with one of the ubnt edge products. I just don't know enough networking to decide which one. I'm leaning towards the ERLite-3 but I'm looking for recommendations.

I would like to have the ER configured to have 2 separate LAN networks (is this what VLANs are?): 1 for the office (i.e. 10.0.1.0) and 1 for the guest wifi network (192.168.1.0). After reading the AirOS manual I think the only LAN side features I'll use are DHCP, DNS, Firewall/NAT, SSHd and NTP. It would be really nice if I can monitor total boadband usage through vnStat, SNMP or a custom script. I want to know if I'm approacing the data cap imposed on us by our ISP.

Can anyone tell me if the ERLite-3 will perform well in this application? Will I be able to use hardware offloading? Is there a better option?

Thanks,
Mark