We were in WDW on our honeymoon last year over the 4th. I will admit I felt the same way as your wife, I HAD to see the fireworks in the MK on the 4th.
It was stinkin' hot, which isn't a big surprise for Florida in July. It was wall to wall people all day. We actually managed to do a few e-ticket rides using fastpass and some minor ones, but we didn't get a whole lot done. We had long waits for everything including the bathrooms and the fastpass machines (never had those before). We spent most of the day in the shops.
Crowds got unbearable about an hour before the fireworks. You couldn't even move through the hub/main street. We got a place on the pathway towards Tomorrowland. I tried to go get some water for us, it took about 20 minutes to fight through the crowds, and wait in line for water!
Fireworks started about 5 minutes late. They do Fantasy in the Sky for July 4th, not Wishes. The fireworks lasted about 10 minutes maybe 12 minutes. No tink, nothing too spectacle. I didn't even see many going off around the park. I was not impressed at all. I was so disappointed after all the waiting and crowds we endured.
When we came back, I inquired about the lackluster performance here on the boards. There had been some bad weather that passed over the area, so that might have affected some of the show (though I never thought it affected anything other than Tink during the rest of the year) and apparently there were some fights and crowd control issues. So, the fireworks may have been abbreviated. In any case, I was disappointed and thought Wishes was MUCH better and didn't require all the hassle. I wish we would have gone to Epcot instead (and probably will if we are there again during that time frame).