Without a doubt, Singapore will be the cleanest place you visit while in Asia (since you're not going to Japan) so take advantage and hit the food stalls since they regulate them. Singapore is known for nonya cooking (a combination of Malaysian and Chinese cooking), and it is delicious (basically, you are going to be in food paradise in Singapore, Thailand and Vietnam). Definitely try toast with kaya (coconut jam) and if you've never tried it in Texas (you can find it anywhere in the US with any kind of Chinese community), bubble tea (flavored tea with tapioca balls). Bubble tea will be found anywhere in Singapore's Chinatown (which was where I stayed and it was pretty central).
Singapore is famous for its Bird Park, and I liked it well enough (though the "birds of prey" exhibit was closed when I was there...rats!)....I LOVED the Chinese gardens. (You should visit the Chinese or Japanese gardens there at least to take some photos for your mom Bill). Singapore tries to market itself as a place to get good deals on shopping, but don't believe it. Having said that, it will probably be the best place to stock up on English language books until you get to Hong Kong (Thailand has a fair amount, but nowhere near the selection of Singapore or Hong Kong)- but they won't be cheap.
Finally, got to hit the Raffles Hotel to drink Singapore Slings where they were first invented!