Aloha,
I have a friend that is going to be coming to Kaua'i in March/April and doesn't SCUBA dive but does want to snorkel.
Anyone have any recommendations on where to go and if there are any spectacular shops if they want to go on a day trip?
Aloha!
Should be great snorkeling during that time frame, barring any unforeseen bad weather. If your friends are beginner snorkelers, I definitely recommend starting at Poipu Beach -calm, protected beach with lifeguards and plenty of fish, sea stars, sea cucumbers, and turtles. If they are already comfortable in the water, one of my absolute most favorite places to snorkel is Lawai Beach. I go there w/my nieces every summer and we always have a blast and see tons of aquatic life.
The north shore might be good that time as well, as nematoid mentioned. I highly recommend checking with one of the local snorkel/dive shops before heading up there, though, as conditions can be treacherous if the weather is not cooperating. If conditions up there are good, Tunnels, Kee or Anini beaches are my favorites. Again, calm waters protected by an outer reef, plenty of fish and usually quite a few turtles.
If your friends want a guided snorkel tour, Aquatic Adventures has a best-selling guided snorkel tour we call the Turtle Tour. It is awesome
But otherwise, we're just as happy to provide tips on snorkel sites, directions, weather conditions, and rental or retail snorkel gear. And our shop is within walking distance of Poipu Beach.
Best of luck to your friends as they plan their trip!