Less than a 3 hour direct flight away from Hong Kong is Cebu, a group of islands in the Philippines. If you're looking for a sunshine beach break from HK then Cebu is worth a visit. There's not much going on so I would recommend a 3 to 4 night stay.
With kids, the Shangri La Mactan is the hotel for you. Don't count on designer bedrooms and top quality nosh but do enjoy the kids haven of numerous pools, white sandy man made beach, swings, ice cream shop, expanse of grass to run around on and softplay. I'll post my Tripadvisor review next.
We booked a Cathay holiday package and got a reasonably priced deal for 3 nights. The hotel babysitting service was great (nothing worse than depressing nights spent sitting in the dark after your kid has gone to sleep!) and we left relaxed and recharged.
If you're looking for a slightly more upmarket room, treat yourself to one in the Ocean Club (still not 5 star standard I don't think).
Whilst the Shangri La offers you very average food, venture out to the Abaca Boutique Resort for a delicious dinner.
The driest months are mid Feb to April. We went end March and enjoyed stunning weather