I think modern Pentium CPU's, and even Celeron if the budget is tight, are capable of handling the tasks that users such as your father would use. This could save some money.
The bad reputation of the Pentium and the Celeron originate from the fact that the Pentiums and Celerons from yesterday (or some years ago) were genuinely slow. They were the bottleneck. But that has changed with the new CPU's. And even if a new Pentium CPU is the bottleneck in an SSD-equipped system, I doubt that any users will notice the difference between a Pentium and an i3 in regular use.
With such an efficient CPU you won't need the cooling power of a tower cooler. A cheap, down-blowing cooler will also do the trick. I even believe that a cheap cooler such as the Arctic Cooling Alpine 11 Pro (10-15 USD) will be able to cool the CPU inaudibly. I have one of those cooling my triple-core (95 W) AMD CPU while running [email protected]
in the background. And I can't here the fan running at all!. The CPU temperature is currently 51 C. But make sure you buy a version of the AC Alpine cooler where the minimum fan speed is 500 rpm.