The next time you're on the Big Island, check out the Ocean Rider Seahorse Ranch. An aquafarm that raises and sells seahorses, Ocean Rider offers tours of their facilities, during which you can actually "shake hands" with a pregnant seahorse, which as you probably know, are the males in the bunch.
The one-hour tour of the 3-acre farm is led by a certified biologist, and there are 3 tour times a day. And if you and the kids love these delicate sea creatures enough, you can buy them, as the ranch raises them for aquarium environments. The only caveat: you'll have to wait until you return home, since the ranch doesn't sell them in the state of Hawaii to avoid having seahorses released into the local waters. That, the special care involved, and the pricetag - most of them are upwards of $100 - should help to avoid any impulse buying.
The Ocean Rider Seahorse Ranch offers tours from Monday through Friday at 10, 12 & 2. Reservations are required; you can either purchase tickets online or call to prepay and reserve a spot. Adult tickets are $35 and children's tickets, good for kids 4-11, are $27. Note: kids 3 and under are free but are not allowed to touch, shake hands with or put their hands in the water with the seahorse, so if you've got kids in both age groups, you might be better off waiting until the youngest is at least 4 to avoid tears. To purchase tickets or for more information, call 808. 329.6840.