I agree about the pictures and having a special backpack. I just had a little photo album made up on Shutterfly.com for our daughter (who will be two when we move next month) with pictures of our house here, her daycare provider here, family members, their houses, the park, etc.

Acknowledge that you miss people, it's okay to be sad, and let him act on it - "I miss so-and-so too. Let's draw a picture for them."

We talk about how we are taking a big trip and going to a new house. How the new house is in Hong Kong (fortunately we have a few pictures of our apt complex) and I have pictures all the neat things we will see here - boats in the harbor, pandas, pictures of the HK buses - she loves buses.

Good luck!