The star idea is a neat one, although there are several different star registries and it's really not much more than a very genteel and enjoyable scam. (I say that as the proud purchaser of a star for my parents, a star for my brother, and one for myself as well.
All three of our stars are clustered near the leftmost star in Orion's belt, so be sure to wave when you see us!)
Years ago when my best friends had their first baby, I was working in the sign industry, and I invented something that is now being done quite a bit:
I made them a good quality vinyl banner, seven feet long by 30 inches wide, with a pocket along the top edge to hold a wooden dowel on a cord, so the banner could be hung vertically. Running upward along the left edge were the words "Happy Birthday" and the child's name, in a large italic typeface (because the slant makes it easier to read on the vertical).
Along the right edge were marks for feet and inches, all the way up from zero at the bottom to the six-and-a-half-foot mark near the top. The idea was to hang the banner up on every birthday and mark the child's height at each age!
Enclosed with the banner were some pre-cut peel-off vinyl stars (about four inches across) that the parents could use to mark the child's height along that right edge on his birthday every year... plus some Sharpie markers, so they could write in the exact information directly on the banner (4 feet 3.5 inches or whatever), plus any special notes they wanted to make.
I gave the banner to them rolled up inside a good sturdy tube with colorful fabric glued on it all around to make it pretty. They loved it -- and of course, they use it every year!