You guys would probably never do it, but there are frequent public buses to Khao Lak up the main highway past the airport. Prices range from 50 to 100 Baht depending on the bus. All you have to do is get a songthaew or minibus to take you from the airport to the nearby bus stop. No need to go into Phuket City. The buses have "Takua Pa" or "Ranong" written on them in roman lettering. If you take a Ranong bus make sure it's taking the route through Khao Lak.

And if you really want to "help someone" you could contribute the 1900 baht you save to the school in the town of Nam Kem, just north of Khao Lak, which was seriously devastated in the tsunami.