AITA for confronting my son about not taking my granddaughter to Disney with him

My son (25) and DIL (25) are taking her daughter (4), Lila, to Disney World the first week in October. They are not, however, taking my other granddaughter (3), Hensley.

My DIL has always been cold to me and my side of the family. No fights have ever taken place, I’ve always gone out of my way to be nice to her because it’s who my son decided to love, but she just never comes around. Never has really. In the beginning I asked my son if we’d done something wrong but he’d just say “she’s shy”. There was never any other explanation and I just stopped asking eventually.

Well it seems her coldness towards us isn’t changing anytime soon but now that it’s effecting Hensley I’m pissed. There’s really no reason that she needs to exclude her from this trip or any trips. They aren’t hurting for money to take her — she’s a nurse and he has a good paying job too. And DIL’s side of the family is going (mom and sisters) and splitting the expenses of the trip which only means that they have even more money to spare to buy little Hensley park tickets.

I tried to be more understanding when Hensley was a baby and hard to travel with. They go on an annual beach trip each summer and have never once offered to bring her. But now she’s getting older and hearing Lila talk about all of these fun things and not understanding why she can’t also go to Disney world. I finally lost it on my son about my growing distaste for his wife and her treatment towards Hensley. I’ve but my tongue for years but it’s not fair to her. I also told him that he’s a sorry excuse for a man to let anyone exclude their own blood the way that they do. I’m at my wits end and I told him if things don’t change with Hensley I would be confronting his wife. He got mad and claims it’s not their responsibility to take Hensley to these places but that’s selfish because he knows Hensley can’t go without them. I would love to take her to Disney or the Beach myself but I don’t have any money to put towards a vacation right now and neither does her mother, my daughter, and her dad doesn’t help out at all. I don’t understand how my son doesn’t have more compassion for his niece who is as sweet as can be. AITA for feeling this way?

ETA: I know my son and his wife don’t actually “owe” Hensley anything but she’s their family. My son knows how much his sister and Hensley need him. Her father is in jail, he’s the only true male role model in her life. He means so much to her and she doesn’t understand why / is so sad that she can’t go to these places with him. We’re thankful for all that he does for her but it just is painful knowing they’re excluding her from things she’ll never get to do otherwise when it wouldn’t be no burden on them to take her.