If your long term goal is to work on using you sons own values and giving him choices etc I think this is good learning tool to help him tune into that. However, rewards charts don't work in the long term research shows that children loose intrinsic desire to learn. Children expect some external reward every time and when the rewards don't get bigger or better it looses its effectiveness. I highly recommend a book called Unconditional Parenting by Alfie Kohn, It tears up everything you thought about rewards/positive reinforcement and of course traditional punishment. What I loved about it was that it the first half was all the backed up research based evidence and studies on children and teenagers and what discipline or reward system was used.

Wanted to hear about the process and the tool you used for the issues you were having.

Will this be a good thing to start with a 3 yrs old kid?

They don't work long term, there should be situational consequences rather than rewarding good behaviour with stickers and look for external rewards.