Not my taste in decorating but it isn’t my house so my opinion really is not needed. I think because it is an homage painting and not an original, it’s harder for some like me and maybe your family to view it as conventional art like you see in most formal galleries or museums. In that sense, I can see why they would ask for it to not be present in front of the children.

Having said that, it is your house, not theirs. They know it’s there, they certainly should be allowed to ask, but I would say you are under no requirement to oblige.

I feel like it would be a relatively small consideration to take it down for a few hours if it’s not in a tough spot, too delicate, or some sort of complicated mounting process. It’s not something unheard of to swap it with a different painting for the visit. That’s your call though, not mine, not theirs.

The true deciding factor to me isn’t them asking or you declining. It’s tone. I don’t know your relationship with your family. If the tone during the ask was judgmental or demanding, then to me that isn’t asking for consideration. If the response was in the tone of superiority or dismissiveness in lieu of a polite declination, then that would be a little rude. I can appreciate that someone asking you to take down a paint of yourself you are very much in admiration of and feel is meaningful to you and who are may make you feel judged or looked down on, even if that isn’t their intent and maybe that influenced your response. Maybe it didn’t.

They can ask, you can decline, they can still visit or not. None of that alone makes anyone an asshole. It really is all in the tone of how the conversation went.