Do you have questions mainly because it is a long trip or mainly because it is to Asia? If you have never been to Asia with young children before, you might want to consider the following...
Depending on the area to which you are traveling, there may not be diaper wipes available at the stores. The diapers over there (if they are availabe) are like the older kind here (shiny on the outside, not really stretchy) but they worked just fine for me.
If you are bottle feeding and your baby likes warm formula, either make sure the hotel provides something for boiling water in or bring your own. Otherwise, you will have to use cool bottled water (as in not hot tap water).
The formulas over there are a little different mixture than over here, so bring your own.
If you are in a busy city, be aware that crossing the street is not the same as here. Pedistrians do NOT have the right of way. SO, if you are worried about your two year old, I say, go for the "leash" with him. Who cares what others think. Make it easier for yourself. I got a cute one for my two year old that looked like a little school backpack. Everyone thought it was so cute to see a two year old with a backpack that they didn't give me any sideways looks about the leash.
I have a Lascal buggy board platform. It's great. Just make sure you get the right kind for your stroller. There are two models depending on how your stroller bars are designed. Do remember, though, that if the two year old is standing on the board and doesn't mind you very well, he is free to hop off and run around as he pleases.
Have fun.