With a GS-13 if you can't afford to do any kind of GA flying you're doing something wrong. I do commend you for attempting to save for retirement and children's college education simultaneously. I don't have children yet, but I wrote off a long time ago the possibility of being able to save for retirement and subsidizing a college education simultaneously,
in the absence of a pension. Yes, I know FERS is technically a 1/3 of a pension, yet still a joke compared to CSRS.
If I were you I'd buy that cessna and fly on the weekends and tell johnny there's nothing wrong with in-state tuition.
At least that's what I plan on doing...
Jest aside, I do suspect if your wife was even a secondary income provider that it would largely alleviate your monthly budget and allow you to fly recreationally. I know as someone who works for and with civil servants, and aspires to gain employment in the system, that said job does give you plenty time off to pursue GA.
Thanks for your candid response, I think that's the kind of feedback the OP was looking for.