^I wish I'd read (and believed) this advice years ago, I might have made a few decisions differently about a couple of family guns. However, as someone who finds himself in the same situation sometimes (sell something to buy something)...I have another idea.
First-off...remember OP-you're asking this question in a rimfire forum where most of us likely have multiple 22s, and our eyes on 2-3 others we'd like to have. Just a guess.

I suspect everyone who read your thread starter, myself included, thought; "what's the issue with 2, 22LR rifles?" Recognizing the OP may only have a DESIRE to own/shoot one, here is another angle;
Unless selling the 10/22 would upset your father in law, I'd consider that he only fired this modern, easy-to-replace, production rifle on one occasion. If that's the case, clearly the man never loved the rifle, or loved shooting it. Or both. No comment on the choice of that gun as a gift (I love guns as gifts!) just pointing out that you maybe shouldn't feel obligated to have affection for a gun that he barely touched. I won't say "Sell" or "don't sell", but if buying/using the tent you want would make you happier than that 10/22 locked-up in your safe, I imagine your father in law would even prefer you go that route.
I justified selling one of my grandfather's rifles sort of on the same premise, and while I'm not nostalgic, he was a successful, and pragmatic man. I wondered whether he'd prefer I keep his old rifle I can't buy ammo for anyway, or, use the funds to buy something nice I'd shoot every week. He would have chose the latter, I'm sure.