Greetings.
Had to chime in on this old thread.
I would suggest that if your child is counting on his/her fingers, why not teach them the
right way to count on their fingers?
Here is a link to the book "The Complete Book of Fingermath," by Edwin M. Lieberthal.
Basically, this method teaches the reader how to use his or her fingers to add, subtract, multiply, and divide -- faster than with a calculator, in some instances.
The right hand represents the ones, with the thumb representing five.
The left hand represents the tens, and the thumb represents 50.
Numbers are represented by placing various fingers flat on the table. For instance, to represent 14, you would place the left forefinger and all of the right fingers on the table (no thumbs, now ...!). Pressing all 10 digits on the table give you 99 (the left thumb is 50, the four fingers represent 40, and all the fingers on the right hand represent 9.
Alas, I never got too far beyond basic addition before I managed to misplace (forever, unfortunately) my copy of the book ... but if your kids are going to count on their fingers anyway, they should do it this way!
Here's a 5 year old doing some rather heavy math -- including adding, subtracting, multiplying, and dividing.
Good luck ......
--gdw