As tempting as it seems to wear tennis shoes with your tux, don't do it. I think it looks ridiculous. If you're 14 years old, maybe give it a shot. In general, don't portray anything that says 'I'm too cool and I don't care.'
“I grew up climbing mountains in Montana and Wyoming and my wife and I were engaged on top of a mountain peak: Hyalite Peak in Montana. It was a 15-mile hike to get to the top of that, round-trip - thankfully, she said yes.”