You can. It all just depends how "fussy" you think the bride/groom will be about it getting messy. If you believe the experience of seeing their guests sign the quilt & being able to take it with the is more important than it being very neat & tidy (to some people, it is), honestly, I'd probably keep it pretty simple & tie it rather than quilting it. Typically the signature quilts I've seen either have square/rectangle piecing (SID so easy to sign without having to go over stitching) or applique (hearts & leaves seem to be especially popular). Try to get signatures as early on as possible & keep the quilt signing table away from any food, drinks, crowded areas or the front door.
If the bride & groom are more particular about having everything looking all nice & neat on the quilt, you could try to gather signatures or quote ahead of time. I had a neighbor whose mom did that for her. She got some people to sign in person & set-up an eVite for the rest of the guests to post their favorite quote about love that she would copy onto the quilt with their names. The fabric for signing was pressed to freezer paper on the back to make it flat. For the front, she bought this giant rectangle hole punch (2"-3" probably) that she used to punch a hole in the middle of the freezer paper & then applied that as the "signing window" to the front of the fabric. I wish I had a picture of it because it was the loveliest quilt.
As far as what pen to use, Peckish put together this nice side-by-side comparison of different pens:
http://www.seamstobeyouandme.com/201...inal-decision/
Other inks will stay if you apply either Textile Medium or Aloe Gel (I use 1:1 ratio with water) -- but then that is sticky & needs to dry flat to set for several days before washing.
Lately, it seems like most of the weddings I've been to prefer not to receive gifts on their wedding day. They have so much going on that day that they enjoy receiving the gifts (other than money) either shortly before or after the wedding.