When looking at players try for one tht has a line out socket out not just a headphone socket.
The reason being the line out socket will have a stronger signal and will give you a better recording. You can get by with only a headphone out socket but you'll get better results with line out.
The AC adaptor is a good thing to look for also. If you're doing a lot of tapes you'll go through s lot of batteries. If the player does not come with one but there is a jack for dc in you can get a universal AC adaptor to use with it. You'll just have to know the voltage it needs.
Audacity is good software, I use it myself. It's a bit complicated at first but for what you seem to be doing you can ignore most of the features and just concentrate on basic recording. Figure on making a few test recordings to get the hang of it all.
Make sure you use good names for the files you create. Come up with some plan before you start and stick with it. Nothing worst then having a folder full of dozens of recording files and the only way you can figure out what is in each is to listen to it!
good luck
regards
PS I can relate to the difficulty in finding those plugs in the back of the Mac. My eyes have a couple of years to go before they hit 70 but flashlights definitely required. 😀