All I can tell you is he is three and lives near a beach. my immediate thought was beach toys but he probably has tons. Still, beach toys!
anyway, I appreciate any suggestions.
I got this for a relative’s 3-year-old’s birthday a few weeks ago. It was a big hit, even playing with it just at the water table on their porch. For the record, I played with it some, too, and thought it was pretty cool. So age range: 3-50. 
Picture books always make great gifts.
Any Super hero character. You might call his Mom and ask what is his favorite. Gift certificate to Build-a-bear workshop.
Price range?
Age appropriate puzzles good, to a good wood (maple ideally) block set if wanting to spend more, to a new Brio or Thomas train or special track part if they have a set.
Beach stuff? No.
Thomas Trains are loved by every little boy I know.
Realistic model airplanes, like a miniature real-looking replica of a 747.
that does look like fun 
price range is $15ish.
Play-doh construction set of some kind, like the fun factory.
Bubble machine or pop up tunnel (or houses!)
Depending on your friend and her view of sidewalk art, outdoor chalk is always fun too.
Strong upvote for the Gruffalo
As a parent? Nothing that makes noise or has lots of parts. Previously as the single uncle, a drum or bicycle horn.
Something electronic that makes loud and repetitive noises when you press a button.
You don’t have to live with it…
A puppy or a drum set
My nephew and niece really liked Stomp Rockets when I bought it for them at about that age. Be warned that it’s very easy to lose one of the rockets on the roof or in a tree, but if you fire straight up in a clearing, you can generally avoid that.
A flashlight. Little kids love them.
Any age appropriate music creation device. 
thanks to all those with good suggestions; even if I don’t buy Stomp Rockets I’m just a little bit happier to know they exist. 
I’d check with the parents before getting play dough - that shit is hell to get out of carpets