😂 good question... I think Bombadil is older than treebeard, especially treebeard as an ent; he was one of the first trees taught to speak by the elves (that's how they became real ents) but as bombadil says that he already was there before stars and whatever, he has to be the older one (if he does not lie, of course; it would solve many (though by far not all) riddles if Bombadil would just be some crazy guy thinking he was the best 😛
And about Goldberry... hm... She might be something similar to a Maia because she says this stuff like that she was the daughter of this riverwoman and so on.
In one of the Letters, Tolkien says that she "represents the seasonal changes of the lands."
I assume that she was a maia of Ulmo (or of one of Ulmo's female Maiar); daughter doesn't have to mean that she is the real daughter, this can also be interpreted as a daughter-in-mind. Maybe she was also someone who drowned in the Withywindle and was sent back by Ulmo or something...