According to French and Raven there are 5 bases for power: Reward power, coercive power,expert power, legitimate power and referent power. As a parent or grandparent you have the advantage of having all five.For example when my granddaughter comes to visit she knows

1. she will be rewarded: gifts, clothes, money, affection

2. possible scolding if she does something very naughty

3. she is shown how to write numbers, the best way to catch a ball etc.

4. Obviously she accepts as legitimate any requests or orders

5. Obviously she admires and wants to do things that I can do bit she can't