If you have a genset with a remote radiator you will still need an enormous amount of ventilation air to cool the generator room. I recently did a generator room with two 2000kVa water cooled generators and required 25,000L/s ventilation to maintain a 18 degree temperature rise in the room over ambient temperature.
You need to talk to your generator supplier to confirm the heat that the generator radiates into the room, determine the maximum temperature you can allow in the room, your design ambient temperature and then calculate the air flow. Plus you need to make allowance for combustion air which won't be as large, but is not insignificant either.
The next issue will be acoustics and large airflows need large attenuators!