Should I visit Kauai or the Big Island when travelling with my husband and 1 year old son?

Without a doubt go to Kauai. You said that you don't mind hiking, I don't know about the Big Island but Kauai has some of the best view that you will ever see from your hiking trails. Also to drive from south shore to north shore only takes two hours (at good times). However I must say that 5 days will not be enough. I could go on a lot longer but if you get the ultimate guide to kauai (a small blue book sold almost everywhere on the island and on amazon.com) you will see just how much there is to do there. I hope this helps.

I live on the island of Oahu but I've been to both Kauai and Big Island a lot of times and... I definitely recommend Kauai. The view there is awesome and something about it just makes you feel really spiritual.

But really do your research on the hotels there.

Kauaii. You won't be in the car very long on any of the islands. The north end, up by Princeville, is stunningly beautiful. Plenty of places to play on sand and to hike.

go to kauai! you will not regret it. its so beautiful there. great hiking places, lots of trails. words cannot describe how breath taking that island is. i highly recommend to go there. its such a great vacation spot.

i just returned form there kauaii was disapointed others find it ok i think ohau is the best