What your in-laws do for a living? Tell them to do it for free for you. That will settle the matter.
I have a photographer friend helping me out, I pay him with a big discount he offers me and I help him build websites, which is a huge bonus for him seeing my work products are more expensive than his on the market.
So if they weren’t willing to pay you, trade for something else.
Do something you won’t regret when you are in your 70s. If you don’t do this and you know it will eat away at you, then you have to do it. I have been there before where you ate now, and I am telling you, it has been nothing but great and fantastic memories.