The OP does not mention having taken this fireworks cruise at WDW.
She mentioned seeing fireworks over the beach, in Maine, at the 4th of July.
She also mentions 'healing' and grieving her mothers death.
I don't think I am seeing any real correlation here????
Not with the memories from Maine... And not with a proposal.
The OP does mention how she has negative opinions of love, marriage, etc...
I think that is a huge factor.
While I have my own negative experience with a man who was 'too close' to his parents.
I am purposefully putting that aside, as, whether anyone believes it or not, I can usually be very objective.
I am holding off on any judgment of the son, based on these two things...
1. His objective is to move out into his own place with his fiance.
2. He did have second thoughts, has changed his mind, and does not want 'MOMMY" there for his otherwise private proposal.
The OP has not specifically mentioned that her son is hoping/expecting that mommy will pay for his private fireworks cruise. I will say that, IF this is the case... I am squarely in the RUNNNNNNN!!!!! camp.
The bottom line is this....
HE SHOULD PLAN HIS OWN PROPOSAL, AND DO IT WITHOUT THE OP THERE.
This many pages later, I am wondering, then, what is the problem?????
Tons of different options for a proposal.
Fireworks are a different and separate, and less important issue.
I am seeing that the real issue here is that, instead of working this out... saying "okay, good, son!!! I hope it all works out wonderfully!"
That there is really any issue at all??????