Should I buy a separate Router or utilize routing functionality on Fortinet 60E's for small business Network Upgrade

So I am about to pull the trigger on some 60E's for our small business, but I wasn't sure if I should buy some stand alone router (such as Edgerouter or USG) or utilize the routing functionality built into the units. I asked this question on Spiceworks and am getting conflicting advice.

Some background information - Two locations: Corporate Office - Seven users, Plant - Six users. - Will be buying four Ubiquiti AP's and two POE switches.

Let me know if you need any additional information.