I can't comment on juggling work and online classes but, I went back to school full time in 2012--at 41 years--old to finish my math degree. I'm now a graduate student and I love it. My point: give it a shot, if only to satisfy your curiosities. You may go back and not like it; then, you'll know. Otherwise, you'll always wonder.

Either major that you're considering are wise (for a returning student). I strongly urge you to research the different types of accreditation. If the online school you're considering awards credits that don't don't transfer to state universities, I'd avoid them. I might be wary of an online engineering program since those programs are typically pretty lab intensive. Good luck, man!