I take my two ice skating ( 2.9yr old and 10 yr old). It works a bit better if we invite another 10 year old / friend, more fun for my son (the 10 yr old). (two year old is just learning to skate, so its a bit of work for me, but the fresh air and exercise and concentration/distraction is for good for me - although I wish I could just skate around with my 10 year old.)
This age gap is tricky, I relate. BUT best try to do something. Your 9 year old, I would think, even if he doesn't want to do anything, that you should make plans and do something with them it will be good for you, and then you can all come home a veg out in your own ways ... but feel good about it because of the earlier outing. Bring a friend along for the 9 year old. Museum, winter festival, easy dining place, play area, a walk/hike with the stroller. I tend to try to do something for the three of us, with the promise of a play date for the 10 year old later. Or, the 10 year old can now call up some buddies, meet at the park and play, and then I walk down there with the 2 year old 15 mins later or so.
ANd it is ok to do nothing on the weekend, after working all week. But a bit of an outing is always good for the emotional state. Do little outings with each one, individually; let your husband watch one, and go do an age friendly thing with your son - rebond w/ him and then set up a play date in the afternoon for him, and then come home and then go run an errand or do some age friendly thing with the little one while older one is playing with friend or while your husband watches the him.