Similar here.

Looking back at pictures from really not that long ago (less than 5 years) to before kids or the first year of the first kid and one of the overriding comments both me and wife have are "We look so young!". We have two aged 3-to-5, and its been hard but not that hard, especially now that there are no nappies/diapers and they sleep 10-11 hours straight overnight and we pay for gardeners, cleaners etc and pretty much do our usual 9-5 as we did before kids.

FWIW though, I would say that you don't need a gym membership. I try to run/jog/saunter a couple of times a week - its free and easy to do. Getting started is as easy as putting some shoes on and stepping out your door - no set up, no memberships, no travel to get to the place to do the running etc. You don't need to go buy special shoes or anything - just something vaguely appropriate will be fine to get started with for short distances and steady pace.

Its what your body has evolved to do, and I think there is a good mental-health aspect to just going out on your own and running and letting the mind wander. I personally don't especially "enjoy" running, and it is sometimes hard to persuade myself to actually go do it, but once I have started and I am 5-10 minutes in, it's quite nice.

Good luck