Yes, a switch is a good idea. One advantage is one computer can see the other's files if both are connected, powered up and properly configured for file sharing, thus allowing exchanging/copying/transferring files
There are a whole bunch of sub-$10 4-port switches available on Amazon, although I'm not sure about the quality. But that will basically allow one port in and three out. You don't need to worry about which port plugs in as it just takes care of itself. But here's one:
The main issue is that they're going to need a power supply, and one more wall wart can be an issue depending on what else is there. On top of being kind of an eyesore compared to having more ports in the first place.
There are a whole bunch of sub-$10 4-port switches available on Amazon, although I'm not sure about the quality. But that will basically allow one port in and three out. You don't need to worry about which port plugs in as it just takes care of itself. But here's one: