You can get a y harness and plug both fans into one channel. I know you are not planning to race, but if you do you will need an open channel for the transponder so you can get your laps counted by the scoring software.

As for needing a fan, that will depend on many factors (timing, esc settings, how hard you drive, ambient temperature, and gearing). There should be gearing suggestions in the manual for the car or esc/motor. Running fans will let you run back to back batteries without having to wait for stuff to cool back down. You could also add an external bec to give you more flexibility to add fans.The battery and charger technology has come far enough along that you can charge a battery faster than you can run it down, so you can run nearly interrupted with 2 batteries if you run fans.

There is a gearing recommendation chart from castle that will give you a gearing range. You might have to do some math to figure out where to start, but that is all you need because once you run the car you can see if you need to change gearing. A few pinion gears a couple teeth apart gives you some range without spending an arm and a leg.