Publish Fortinet_CA_SSLProxy certificate on Captive portal for "public" WiFi

Anyone who can help me out with this one.

I am trying to deploy a fortigate environment on a vessel to give a big crew (100+) access to the internet during their off hours. Due to lack of bandwidth Satellite connection of 2Mb, I need to set a lot of tight restrictions so for that I need deep SSL inspection. As the crew members all use their own devices I need a "user friendly" way to have them to install the Fortinet_CA_SSLProxy certificate on their own devices. As they will all need to log in (to prevent too many users / devices on the system) I thought it might be a good idea to publish the Fortinet_CA_SSLProxy certificate on the Captive Portal page with a small instruction how this works on IE / Chrome / Android / I phone including the certificate to be downloaded on that very same page. (As this is an isolated network I do not have any other devices / servers in this network so I prefer to have everything installed / accessable on my 101E Fortigate) Anyone knows if this is possible and how / where to begin ? Thank you