Some children get it, some children don't. Here are some tips I have written to give you some advice about giving pocket money to children.
Tip 1: Give each child a dollar per age, so if you have a child who is 5, they would get $5 every week or once a fortnight.
Tip 2: Buy them two money tins. One which can't be opened until the future, the "savings" money tin (or it can be stored in the bank under their name, whatever you choose to do) and have a separate money tin for "spending sometimes".
Tip 3: Don't let your child bring their spending money every time you're at the shops. Once a month let them take out a maximum of around $10 and let them buy something if they see something.
Tip 4: If your child really wants something (a new toy, book, etc) don't give in and buy it for them. Encourage them to work towards it and earn it. Get them to save up half their pocket money until they have enough and then let them buy it. It'll feel good for them to have worked for something they want.
Tip 5: Think about what your child really wants to spend their money on. If they seem to really want to use their spare money to buy treats like chips and chocolates, pull the reigns. Don't let them buy junk food (a little lollipop once in a while never hurt) but if your seven year old is scurrying down the supermarket aisles with packets of chips, biscuits and ice-cream in his basket then step in.
Tip 6: Teach your child the value of saving money. Let them know why its important to save money and how if in case one day they really need it, they'll have money saved up. Teaching children early about saving money and trying to resist the urge to buy silly stuff with it, when they're older they'll value money as well and be good savers (we hope)
I hope these tips have influenced you a bit, they have worked on my siblings so hopefully they work with your children.