Congratulations!
Reminds me of my story - about 4 years ago I was searching with my now ex-girlfriend for a geocache near the beach and found GZ to be this amazing scenic spot overlooking most of the beach. It was breathtaking, and I knew that I would one day be proposing to my wife there (thankfully it wasn't the girl I was with at the time! )
The cache is GC1WCAK. Roughly three years later, I proposed to my wife there on 04/28/2013.
------
Anyways, I'd suggest you make the cache page, and wait to submit it until after you've proposed. Hide it well (obviously) and make sure you hire someone to record/take pictures! They're worth looking back on later down the road!
Good luck!