Family of 4, 2 adults and 2 older teenagers want beautiful beaches, great snorkeling, rainforest, hikes, zip lines, kayaking in beautiful waterways, mountains, biking, culture, history. Any suggestions?? Thanks!

Kawaii

i suspect nevisian meant kauai in hawaii.
in the carib you should look at st. lucia or jamaica. both have all on your list, although some do not consider st. lucia's beachs to be totally wonderful(sand is not blindingly white)
if you wanted to go further either belize and costa rica would offer all you are looking for.

Thanks Virginia. Another question, we were told Costa Rica in July is too humid & hot to enjoy, go in the winter/spring months. Do you agree? That is why we were looking at the Caribbean.

I've never been to Costa Rica in the summer, I guess 'too hot and humid' is a relative thing. We spend lots of time in Belize in September, and it certainly is hot. Depends pretty much on your own tolerance for heat. If you spend your life in air conditioning and really don't like being out when it's hot, it will be too hot.

If good snorkeling is a priority, I'd give Costa Rica a pass.

Generally, the islands with the most beautiful white sand beaches aren't the ones with the lush jungles.

jeanh is right. neither jam or st. lucia offer great snorkeling but they do have some.
there are also zips on antigua (stunning beaches) and st. marteen.

perhaps st. john would be good. it has only a litte culture/history and no rainforest/zip line but hiking is good, beaches are great, kayaks available, snorkel outstanding. most people rent villas. two big resorts are westin and pricey caneel bay.
or kauai...

i've tried bahamas with my family, and all of us enjoyed our vacation.very much satisfied may i add. lots of activities you can do there like bicycling, parasailing, kayaking, boating, island-hopping, snorkeling, eco-adventure, and windsurfing. i am a hundred percent sure you'll love it there.