Hard to stay "up" when you continually get knocked down
I hear you, Tom! And I can empathize too... wanting close knit family and unconditional love... but it just doesn't always work out like that.
I've also felt ignored by family at times and felt my daughter was being slighted over her younger cousin (the perfect brothers daughter). I eventually confronted my mother about it... several times. It changed her some, but not my step-father. My sister and I get along great on the phone, but put us in a room together for more than an hour or so and the cat claws come out. My brother... he used to ignore us until he had to visit with us.
Your therapist is right... if you ain't happy... ain't nobody happy. So do what YOU want to do and what you think is best for YOUR immediate family. If it's joining everyone at DisneyWorld, then great... go and get the best possible deal you can. Maybe you'll be able to confront your family about their attitude and get it out in the open.
As for your wife's sister, surely she understands the money and work/school issue. So put it on her plate... if she can work everything out so it's all smoothly taken care of when she's gone and the trip can be budgeted for, then great! But if not... then maybe she can delay trip until summer when kids don't have to get to school?
You've done such a GREAT job on your weight loss journey... and you're learning that it hasn't made your world perfect and happy. But you lost the weight for your health, right? You lost the weight for you, not for your wife or your parents and sisters? Losing weight won't be what makes you happy, Tom. YOU have to make yourself happy.
I truly wish you inner peace and happiness!
It's easy to give advice when you're not in the situation, but I am the same way: caring for everyone else and putting myself last; and lots of therapy to try to correct that. That being said, if it WERE ME:
I'd not worry about grandma, sister-in-law, etc. I'd get four tickets to Disney, get on that plane as a family and don't look back. Concentrate on the four of you and see what can be done to bring you all together. Sometimes worrying about extended family, especially when they don't seem concerned about you and yours, is more destructive to yourself and your immediate family than you realize.
Good luck with your decision.
Terri