Tables for Kids
One of the problems table tennis coaches face is that kids aren't really big enough to play table tennis on a regular table until they are about 6 or 7 years old. Before that the table is simply too high, often about shoulder height. Tennis had a similar problem in that their courts were too big for kids, who were expected to cover the same amount of ground as Roger Federer. They solved it with QuickStart Tennis (5:35). As a long-time tennis player on the side, I've actually helped with these tennis programs, where they often have a court full of kids in the 3-5 year old range. There's no reason why table tennis can't also start in that age range - except for the size of the table. In fact, with smaller rackets and courts, table tennis should be easier than tennis for these kids!
Sean O'Neill has been a strong advocate for shorter tables for younger kids. He argues that shorter tables is both good for very younger players (such as the 3-5 age group) as well as for slightly older ones (such as under 10), where the height of the normal table might lead to bad habits while a shorter one would lead to better technique. Here's his article (with pictures) on the subject, Helping Young Kids Learn to Play with Correct Technique, Balance, and Power.
Here are two videos he has on this, where the DHS Rising Star Table is featured. It adjusts to four inches lower than a normal table (from 30 inches down to 26).