Is this your first tax season?
It will depend on how much your firm works through tax season. If you're doing 80-100 hour weeks, you'll have a rough time doing school around that. If you're doing 50 hour weeks, sure, you can do school around that with no problem. If you haven't been through tax season at this firm before so don't know what to expect, then it's harder to know.
Also depends on how much time you need away from work and school, aka how long you can keep on keepin' on before you run out of steam. For some people, due to their health, their family commitments, or their mental makeup, they might need a couple hours every night and at least 1 day per weekend that's free from work and school in order to keep up the grueling pace of their work and school life. For others, as long as they've got time to eat, sleep, and shower, they don't need anything else.
There's 168 hours in a week. If you spend 56 (7×8) sleeping, and let's say 60 working, plus 7 (7×1) eating, showering, etc., and 4 (6x.67) hours commuting, that leaves you 41 hours a week. If you're able to essentially go 24/7, then 41 hours is enough to do 2 classes in with time to spare. If you're working 80 hours, then it leaves you 21, and still enough time to do the classes if you can go without stopping. Most people need some chilling time or they'll not be able to keep up that pace. So, I think figuring out how much chilling time you need and how many hours you'll work are critical to determining whether or not you can do the courses.
P. S. If I was you, I'd look for classes with minimal busy work. Something like Psychology 101 seems to me like it might be prone to lots of busy work writing papers, replying to discussion boards, etc., and therefore could end up taking precious time for useless assignments. Just might want to find out before you register. 🙂 Also, I'm presuming these classes will be online; if they'll be face-to-fact, scratch everything I've said, and don't do them. Telling your manager you've got to leave for 3 hours for class would NOT be popular during a first busy season and probably not during any busy season.
.