I vote for the honeymoon.
I'm not a very sentimental person and I don't like the idea of engagement rings, or fancy weddings, or conflating material wealth with romantic love.
But travel is happiness inducing. And there is something to be said for marking important personal dates with celebration.
This is a situation where playing the miles game (travel hacking) could add real value to your life. You could mark the important occasion, go somewhere cool, enjoy a taste of luxury, and save tons of money all at the same time.
And while it might be too late to finance your honeymoon in this manner, it's certainly not too late to start building up reserves for the next such opportunity.
The final point I would make is that cheap travel is often the best travel. The most romantic trip I ever took with my wife was one of our least expensive ones.
We took a ferry to an island off of the coast of Tokyo- where we lived, (we slept on the floor of the ferry next to a bunch of vacationing college kids,) we stayed at a rustic (read cheap) Inn on the island and biked around the island and Bathed in natural seaside Hot Springs, and picked berries, and got sunburnt, and had a fantastic time.
So scrimp elsewhere, travel somewhere beautiful for less, and celebrate your coming marriage. That seems like the smartest play for happiness from where I am sitting.