I'll second the congrats, just think how much fun you will have spoiling the new grand kid
As for wood, I've seen some VERY nice cribs made from both Maple and Cherry, for the very reasons Vaughn states.
When you get more of a concept that you can post, do so, I'm sure we will take a good run at it and try to avoid any pitfalls, after all, the cargo in a crib is a bit more precious that a book on a bookshelf.
Are you looking at a crib that has four sides and stands on the floor, or more of a cradle?
One other thing to think about, if the crib will easily breakdown for storage, if the time between bundles of joy is short, it is not a problem, but one day, if the crib gets put away, awaiting the next generation, well, you would want it to be able to store flat.
Just some random thoughts.
Cheers!