Is this rude to do?

So last month my family and I went on a cross-country trip to visit some relatives we hadn't seen in a few years; cousins, their children, aunt/uncle etc..

We only stayed for two days, but it was such a great time.. because of the distance, and just how my parents/relatives never made much effort to keep in touch, I wasn't close with them growing up..

But this past trip was really great, and I love kids so spending time with my cousins daughter was great fun, as well as everyone else..

Leaving has been pretty tough, though two weeks later and I'm okay with not seeing them for another year or so..

Until I realized this; my parents have a winter getaway house (I'll call this Beach House) in a warm climate, and my siblings and them are going out in early January to visit for a week, while my parents stay for like three months..

I'm also planning on going, though I came up with this idea; I was thinking of asking my cousin if their daughter would want to come with me/my family to spend a few days away from the cold weather..

The plan would be that I will fly down to where my cousins live, hang with them for the day/a few hours, and then me and their daughter will fly down together to Beach House.. and then we'll fly back together. She's three years old and my cousins totally trust me, as they should b/c I'm responsible!

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Would this be wrong to do, like would it be rude?

In a positive light, my cousins could see it as a warm gesture, not to mention being kid-free for a few days would be a nice change I'm sure, and their child would probably have such a fun time.. my cousins have been saying how much she enjoyed spending time with me, etc.

Or would it be rude to ask only their child and not my cousins to come with too?