I think the thing that makes it sticky is asking around to see "what people think about it." In some sense, you're telling them that what they think about it matters, and might change your decision. This is appropriate sometimes--"How about we meet at the lake?" "Well, it's not wheelchair accessible, and Grandma..." "Oh, I hadn't thought of that! Let's just meet at X as usual." But other times it isn't.
It sounds like you and your DH made a plan that worked for you and made you happy, and no, it's not inherently rude to anyone else. If you let other people think they have some say in it, it may change from what makes you two happy. I'm struck by this line from your post: "They wouldn't mind us going to my spouse's instead but the idea of having Thanksgiving sans family is not something my folks are prepared to accept." I know what you're trying to convey, but the thing is--your parents don't have
to accept this plan. Their permission, understanding, etc. is not required. They might not be happy about it, and that might make you sad, and maybe you want to do something to alleviate that, but on the other hand, maybe you don't.
There's a lot of factors to balance in family relationships
and I'm not saying, "Do whatever you want, who cares what they think!"
I just think, if you're looking for a way to get Person X's "blessing" on your plans, that may not happen, because you can't control what Person X does. There's no magic phrase. (There's definitely bad phrases, though!) You might have to make what you know is the right decision for you and DH, and also
deal with your parents/brother feeling slighted--there may not be a way to make everyone happy.