I guess most guests stay at Negombo on the first day of arrival.
Why not take a massage at 8:00 the next morning and go on a sightseeing at around 10:00 after healing the fatigue of a long flight.
Hotel website here from
<How to use 10% discount>
All you need to know is the name of Sri Lank Taxi Service when applying for a massage!
Please use it by all means.