Starting your kids with tennis
This is a question that parents ask tennis coaches very frequently. The answer to "when" is: it depends on your child, but usually they should start when they are four to five years of age.
You may find that very young, but as a matter of fact, the foundations of general coordination are laid very early. So it is important that you do not wait until later when you find out that they have coordination problems already. And it goes without saying that if they do have coordination problems, or even are a little bit overweight, you need to get them started as soon as possible!
To avoid those problems, you do not necessarily need to bring the child to a tennis coach, but make sure he or she does some sport that requires coordination, preferably with a ball. To my experience, a child that has played a lot of soccer and then starts with tennis at the age of 9 will not have big problems acquiring the right techniques and a good playing level.
When the kids start with tennis at the age of 4, a big part of the training sessions will be about general coordination initially, so when the things that the coach has them do seem to be unrelated to tennis, do not worry! Of course, a lot of the time should be spent handling a ball with the racket, even playing little matches in the samll court, but running, stopping, turning, improving balance and speed are equally part of the tennis training session.
Using adequate equipment is essential of course. That means short, lightweight rackets, soft balls, small courts and mini-nets, target markers and so on. A coach or a club without this type of material is most likely a bad choice for your kids.
So when you decide about the "how" or "where", first start with the tennis clubs in your vicinity. Distance is a big factor in the long run, and when the kids have reached an age when they can go or ride their bicycle to the tennis club on their own, you will see what I mean. Short distance also means that theys will play tennis more often, play more matches with their friends and improve faster.
Choosing the right club, you should also take a look at the club's program and at the coach or the coaches. Do they use the equipment as descibed above, do they have enough children at the same age of your child, do they have competing teams, what is the average member's attitude towards children? What kind of group size are the kids playing in (should not be bigger than 4 kids per group)?
And of course, what is the coaches' personality like? Does he "connect" to your child, is he a good role model for him or her? Do the kids have fun on the tennis courts, does the coach seem to have a plan behind the exercises and games the kids do?
You are making an important long-term decision here, so take the time and compare the alternatives.