Router or not to router, That is the Question?

To Start off the post, I am in the middle of a rebuild of the network in the fire station that I belong to. I may sound like I am a Idiot but trying to figure out if a router is necessary. here is the specks--
- unifi AC AP
- a minimum of 8 port switch
- a provided DSL modem (1 Mbps down .5 up)

The main goal is to update the WiFi access across the engine bay and have two networks (using both radios for ether). and the devise in the trucks connect faster and a stronger connection too update and use the Application running on the I pad in the trucks. I am pretty sure I would need one and plan to use a device closes to this one made by pf Sense (https://store.pfsense.org/SG-2220/). for the moment the connection is what I have to work with and hope can get updated too but for now it is updating the WiFi from N to AC specs and removing the rats nest of wire. Any help would be appreciated.

Why not have one network? Routers/AP's. (Access points are routers not running a DHCP server - which is where IP address come from).

Just making sure i understand what you're planning.

1) Some sort of base station in fire house
2) Each truck would have their own wireless radio to connect to the base station
3) Each truck would have wireless clients (iPads, other devices) which would connect to the AP on the truck and then connect back over to the base station in the fire house

Is that what you're planning?

Each truck just hast a I pad no other intermediate networks in-between and one network for just the trucks and the other for members to use the connection.

Then I would say what @anon75264233 suggested would work just fine; set up one network and let everything talk over that. Is there a particular reason you need to have the members and the trucks on separate networks?