My parents moved 2 years ago about 1mile from me so I can be of more help. Dad has dementia, can't drive and has failing health. Mom took him back to their former state of residence to visit other children, 4 times last year, retuned and was sick for months afterwards, and spent thousands of dollars taking my grown brothers and sisters out to eat. She finally made the decision not to travel because of dads health. I manage their money because she cannot (paying excessive late fees, she does not Remy to pay). Yesterday I got a text from my brother that he is driving down and picking mom & dad up and taking them to Indiana, mom had called and asked him to do so. She is going against her own decisions, doctors advice and family members recommendations not to travel or stay longer than a week. Not to mention the whole famy was driving 9 hours to see them over Thanksgiving and this brother has no problem accepting large amounts of money as "gift". I'm so frustrated, this is same pattern and they will return and I will need to cart them to three doctors appt a week for months.
Go see your mom and dad this morning and tell them they need to postpone their trip until after the holidays. It's highly likely that brother talked them into the trip with easy manipulation.
Get hold of mom's checkbook and, if she does go on the trip, make sure she leaves her check books at home.
Make a decision that you are NOT going to cart them to their doctor appointments for weeks after their trip. If they can afford to treat everybody out to eat, travel, give monetary gifts, they can afford cab fare. I'm not kidding either.
You have GOT to change. If you don't, you will allow your parents AND you to be manipulated by anyone in the family looking for a handout. And! If mom or dad should need nursing home care paid for by Medicaid, any and all gifts and reckless unaccounted for spending will drastically effect their ability to receive help.
Mom trusts you enough to put you in charge of their finances...and thus their well-being. Don't disappoint her.