I think what wyndhy said is how I'd approach it. I'm one that's always preferred the card and the sentiment more than the present. Bought stuff is nice, but if you make something by hand it means far more to me.

Going with Osuche... How about some sort of photo? Either something taken professionally of you and the family, all framed up (or take him too) or some sort of collage of photos that covers your time together. Something that says "Look what we've achieved in 20 years".


And I love the tree and bench idea too - sweet!