Stupid question about weird people

[Peoplemakemesigh]

Do you go to McDonald's? I sometimes do. It's the type of place where I'd expect to get a message from someone asking if I'm free and wanted to pop to McDonald's right now with them.

I've been invited there 6 weeks in advance by a difficult weirdo who I happen to be related to. Would it be rude to delay replying to say yes or no until a couple of days before? It won't make any difference to their day, they're coming to the area for other reasons regardless and will only be squeezing me in at their convenience. They're not desperate to go to McDonald's or anything either, they don't actually like it there.

I'd like to tell them to do one, honestly - we don't get along. But "it's family" and it won't kill me to meet them if I'm able to. Don't really want my life planned around it 6 weeks in advance though!

Someone is asking to meet you in 6 weeks. They are giving advance notice to check you are free. Where they choose to meet is neither here nor there, perhaps it’s just the easiest location for them to get to, the place with best parking, the cheapest option where you buy your own meal, or the place where they know it will be limited to a brief meet, rather than a 2 hour lunch.
Really rude not to respond until nearer the time. It’s the meet up they are asking for confirmation of, not the actual location of McDs.
Decline if you don’t want to see them, but don’t focus on the McDs element, and confirm sooner rather than later.