Those sites are NOT to be trusted! Our games are free to download and offer optional in-game purchases to obtain certain items and progress faster.
All purchases available are within the game so they can only be made from the device you or your child are playing. These third-party sites that promise you free game currency, advanced levels, etc. are usually scams and using them is strictly against our Terms of Service. This may lead to a permanent ban from the game, not to mention the high risk of viruses and getting your personal information and account information stolen.