I've been in that some situation before and I solved it by doing a "homemade" gift. That way you are assured yours won't be a duplicate gift and usually it is a appreciated gift even by the wife that you don't know. So whatever type of craft you do make that. I like to quilt, cross stitch and do various other crafts myself. I've done a simple framed cross stitch of "Welcome", and one with their names and wedding date and then had them framed. My hubby has also made the frames sometimes in the past and then he has his hand in the gift also.
If you have the time a simple set of quilted placemats is always welcome also.
The gift basket is always a good idea. Whatever their likes are just make a gift basket. If they like to go hiking or camping make up a basket with a compass, maps, insulated socks, powdered drinks, travel cups, and anything else that would work for that event small enough to go into a basket.
You could do a evening at home for newlyweds basket. Soft music, nice galsses, wine or sparkling cider or maybe microwave popcorn and a couple of movies, nice set of napkins, etc.
Hope maybe these might help. Good Luck!