Not rude: "So what city or site do you plan on going for the next holiday weekend?" Rude: "So what romantic plans do you and your significant other have for the next holiday weekend?" Possibly neutral: "Can I come with you to wherever you are going for the next holiday weekend?" Unconscionable: "Can that mother-in-law of mine that you don't like come with you?"
i think the possible neutral is more rude than the rude one also every rating would depend on the degree of "closeness" (family/friends/relationship etc) i share with said persons thought right now with all the quarantines and lock downs asking about holiday/travel plans might make you look like a lunatic
Stalker: "enjoy your trip with your significant other at the [hotel name] in [name of place], also, be careful of the guest next to the room you will be staying at... *whisper* he likes to peep on his neighbours Also, remember to... (some more stalker stuff)"
The most important question is, how do you know the other person is going somewhere the next holiday weekend ? Were you stalking him ? Normally I would just start the topic with how i am unable to decide where to go for the next holiday, and then ask for suggestions and if they are planning to go somewhere. This way it doesn't feel as intrusive but more like an exchange. From there you can slip in the questions you want to ask while discussing about good places to go.
I never feel any kinds of awkwardness to such trivial inquiries. It's just like asking about weather. I may feel somewhat awkward to some unexpected response though.
You might add "Fear not! If a fiend attacks you, simply promise me your lingerie, and I shall appear to save you! I am always watching over you..."