If your kids are not interested in any way about taking the sport of table tennis up seriously, then I don't think it hurts for you to give them some advice to help play the game. And remember, kids are great at copying visual examples, so they will be likely to mimic your own style to some extent.
So the bottom line is this: if you think your child might want to play ping-pong seriously in the future, invest some money into getting some proper coaching. A good coach will give you and your child an insight into what is involved in playing advanced table tennis, and your son or daughter can then decide whether he or she wants to pursue the competitive sport, or just enjoy a hit around the family ping-pong table from time to time.

