If you want something more... tropical, for lack of a better work, why not head to to Koh Samet ? Much nicer than Hua Hin IMHO and perfect for a 3 day escape from BKK to the beach.
I've been to Samet not Larn, but the photos look great. IIWY, I'd probably give Larn a shot. LINK:
http://kohlarn.com/
Been to both, found samet much nicer than koh larn and, you don't have to go to Pattaya. Always a good city to avoid.