As other posters have asked, why does anyone need 'support' to visit their own adult DC?
In any situation which involves a conflict of interests between people and their preferred scenario, a fair balance has to be sought which results in the maximum overall happiness for everyone, distributed as evenly as possible between the individuals.
Let's assume the DC prefer to spend time with their Dad without the OP present. (Something the OP hasn't confirmed, but for the sake of my example let's assume).
In the scenario whereby the OP joins her DH, the DCs happiness is diminished, and the OP's happiness is diminished. The DH initially will be happier, but he will be surrounded by loved ones who feel uncomfortable and compromised. Unless he is very thick-skinned, this will impact on his enjoyment.
In the scenario whereby the OP's DH visits alone, the OP is very happy, the DC are very happy, and the DH is less happy than were the OP to join him, but he is still enjoying time with his DC so his happiness is less diminished than that of his loved ones in the first scenario.
This is why it's important to ascertain the DCs feelings towards the OP's inclusion or lack thereof...