I got my mom a cool stamped necklace from Etsy with all of the family names on it (this was for Christmas not a shower). It was in the $30 range, but there are cheaper (and much more expensive options) with the same sentinment
Something like this:
http://www.etsy.com/listing/116973988/xl-hand-stamped-single-washer-keychain?ref=sr_gallery_32&ga_search_query=personalize+family+tree+necklace&ga_view_type=gallery&ga_ship_to=US&ga_page=1&ga_order=price_asc&ga_ref=related&ga_search_type=all
I like that it's a very personal thing to give