I agree! A straight razor is indeed a good gift but I also suspect that despite the "coolness" it might freak them out! Get them a brush, soap and mug set. That is a very cool idea. I gave my brother a straight razor, a strop and the wet shaving kit (without a DE... he got that one himself) and he never touched the razor because he's affraid of it... now the brush and the other stuff, he uses a lot. I confess that it brakes my heart knowing that he won't use the razor... mostly because the strop he has was handmade by myself. That is why I think that the straight razor idea is not a very good one. But hey! you can give them the wet shaving kit NOW and maybe give them the razor and strop when you get maried again!
Seriously, though... congratulations on the tying the knot thing!