Wow, first of all I do not envy your current place in life. Second, you've been given some excellent advice!!
I come from two places; a pet owner and a pet care provider in a kennel setting. I'm certain I know what ails your dog given the description and the meds, sadly not reversible
Last October, I sat for the better part of 14 hours with a client's dog, that thought the coughing was due to age, easy mistake if you're not familiar with symptoms.After getting the initial call from our kennel supervisor that Gracie was not acting her usual self (fortunate for us she's been a client for years so we were in tune with her "normal"). I set up an urgent appointment with the closest dependable vet. They begin with the tests and oxygen, none of us were certain she'd make it through the night, vet included. As she would have been unattended at night, I transferred her to the ER clinic that afternoon. The only time I left was to run home and tend to my own two dogs and then went back. if we were going to lose her, I was not going to allow to be without someone who loved her with her. I stayed in touch with her owners via texts and phone calls until they arrived at nearly Midnight.
With CHF, even the smallest changes can be challenging for them. We live in SE Idaho with a considerable elevation, they took her to their cabin once and symptoms worsened, only 1,000 ft difference in elevation. Gracie is still with us today, but like your baby the meds are at their maximum. (Which reminds me, I need to get in touch with her owners and go visit before it's too late.)
Evaluate the quality of your baby's life and move forward from there. Leave the vacation issue out of the decision that needs to be made. Even if you know in your heart that now is the time, it's going to suck! It will suck whether you give her the greatest gift or she passes in her sleep because you love her and she's part of your family.
Even the most educated person will ask all the "what ifs" there are to be asked, so don't get bogged down with that.
Sending hugs to you and yours during this time.