Normally I try to be fair to both sides of a decision like this, but in this case I feel compelled to just make the case for taking the Monroe.
Not that I have anything against the University of Texas, or fail to recognize the benefits of Plan II, and many families and kids might prefer it for various reasons, including financial.
But holding aside the financial side of things–your Texas associates seem just not to understand exactly what William & Mary offers in general, and then on top of that what the Monroe adds.
I could go on ad nauseum, but William & Mary is a pretty special school, particularly among publics but really in general, and for the right kid is truly one of the best possible choices. I don’t think I need to elaborate, however, because it appears to me your kid already knows this. But the thing I would just emphasize is that if you can afford to go to a college that is a really good fit for you, this is precious because it then maximizes the chances you will really thrive in college. And that is so much more important than exactly where you go.
In other words, I am gently trying to discourage seeing fit and academics as two separate things. In practice, they are related in ways that can really prove critical in a variety of individual circumstances.
Then the Monroe is a significant bonus on top of all that William & Mary offers in general.
Just to be blunt, for those in the know it is a valuable resume line. Same with Plan II, but that is maybe something your Texas associates do not know. Then the housing, the special research program, all this is just making it more and more likely you will get the William & Mary experience you are hoping for. Which, again, is about academics as much as fit.
Anyway, that’s my two cents. No bad choices here, but I would definitely suggest your Texas associates should be making as much of an exception for the Monroe as they would for some general Ivy+ admission (in fact I would personally choose it over some Ivy+ schools, but that is a whole other story).