Is there a halakhic obligation to pray with a hat?

And what is the scope of this custom? Does it oblige me (my whole family and I wear a hat and suit)?

In principle, custom is binding. You can make a waiver of vows or move to a place where they don't practice that way, and then perhaps there is room to explain that the custom of the place overrides the custom of the ancestors.
In the margins of my remarks, I will comment that I have always wondered what the benefit of a waiver of vows is in this. If practicing a good custom three times (why three? In the Shulchan Aruch, it seems that one time is enough) is a vow of waiver, then you will be canceled. But we have not departed from the general obligation of the custom of “do not defecate”. And does waiver cancel the fact that they practiced that way or the obligation of “defecate”?
But what can I do if they did practice it, and the custom of Israel is law. And if I do not correct my words, I will not invalidate them (= I will not allow them to take the vow 🙂 )

Perhaps the explanation is that the local custom includes an exemption from the ancestral custom for those who have made a hetra 🙂