I disagree. You obviously DON'T have to suck it up and pay what you need to pay. This isn't a court appearance where your presence is demanded by law enforcement. This is supposed to be a joyous occasion.
A wedding is a celebration, and guests are ... GUESTS. What you're describing (paying for the post-wedding meal, renting your own vehicle, contributing to a rental of a home that you had no part in selecting, the flight) is not what is expected of a guest.
Of course, all weddings have expenses; some have cash bars so that guests are responsible for their own alcohol, but the dinner and entertainment are provided. Sometimes, invited friends and family members are offered hotel rooms at a particular hotel (the bride and groom reserve a large block of rooms at a discounted rate), and the guests are responsible for paying if they choose to stay at that hotel, but it's not required. If a guest wants to stay with an old college friend, or in a budget motel two towns over, or on a park bench, that's fine. If they want to stay at the discounted hotel, again, that's their choice.
The word is choice. You're not getting any. You're being told where to stay, where to eat, how to get from the airport to the wedding venue, and you're being told to pay for all of it.
You have a lot of responsibilities at home. That's your first responsibility. You have expenses at home, and your presence at a wedding is not required.
I'd have a different answer if you were traveling to support your brother through cancer surgery, or if there had been some sort of tragedy. I'd have a different answer if this was a funeral. I'd have a different answer if the bride and groom were showing any sort of empathy for your situation.
As you say, this is a second wedding for two demanding 40-somethings. It seems that they haven't learned respect for people's difficult situations, and concern for others' budget constraints, and it seems that they're selfish enough to "flip out" because someone can't fly around holiday time and pay for a rental car and pay for a rental house that was chosen for them, and pay for their own reception food. I suggest that by agreeing to their demands, you're not doing them any favors and not tending to your own family's needs. Preventing people from flipping out over this type of situation is not your concern.
Let them flip out. Stay home. Send a gift.