Definitely would recommend the Pullman if they looking for a relaxed type of vacation.
Khao Lak is about 2-hour drive from Phuket and the location seems to be quite remote.
They have lovely beaches however they have a small town and using the hotel shuttle to the town would cost about 200 baht per person for a oneway
It’s not as lively as Karon Beach so it’s a very restful and serene location and if that is what the couple wants, it is exactly what they will get. There are also lots of activities for them to get involved in.
With regards to the holding deposit (the funds are reserved, not actually withdrawn from the account) and Pullman requires 2000 Thai baht per night to be reserved on arrival.