Hello Laura,
Welcome to HKBWS! I hope you will enjoy birding in HK, it is a great place. About the birds you wish to see, Spoon-billed Sandpipers are still being seen annually though numbers are decreasing rather alarmingly, however you will still be able to find them in April at Deep Bay, Mai Po if you are lucky, feeding along with stints on the mud flats. We don't really have the Great White Pelican, however we do have Dalmatian Pelican, which also have declined significantly in the last decade, they have been absent these past years from Deep Bay. Storks are rare winter visitors but they do occur. Cranes are super rare in Hong Kong, I don't think we have had a record since a juvenile Siberian Crane landed in Mai Po in 2002.
Other then Mai Po, I suggest you can try Long Valley in Sheung Shui, a patch of farmland that is great for meadow birds and winter migrants such as buntings. It is also just a very pleasant place to walk.
Tai Po Kau Nature Reserve near Tai Po is a good place to explore the woodland birds in Hong Kong, it will give you a glimpse at some South China woodland species as well as winter migrants like thrushes and flycatchers.
Po Toi Island is the place to be in Spring and Autumn, it is a small island situated South of Hong Kong island, accessible by taking a ferry at Aberdeen. It is a major refuelling station for any migrants coming off the sea, it is now a major birding site in Hong Kong annually.
I am sure you will pick up a few more places as you go around Hong Kong, you will be surprise how birds can pop up in most unusual of places (Like the recent Pied Wheatear that landed in West Kowloon Waterfront Park!).
Happy Birding,
Matthew
[ Last edited by kmatthew at 3/12/2013 23:13 ]