Gay people can make good parents but I'm still always going to be suspect of motives. I've seen a lot of straight couples adopt for reasons I find suspect as well, political virtue signalling and the like, quiverful adjacent types looking to indoctrinate as many kids as possible, bleeding heart non-hateful racist liberal types adopting black kids to seem progressive. (You can be a racist that hates people or a racist that loves people but ultimately you are still a racist if you think race is a good reason to treat people differently)

Gay couples, like it or not, are usually physically capable of having their own kids if they really want, does that mean I think they are all in it for bad reasons? Nah of course not. But that doesn't mean that vetting can be ignored.

In this case I might simply say because the person is so old is good enough reason to not adopt even before we get into the trans stuff.