view & cap how much I've sent with my apple ID

I would like to easily view how much I have spent on apps and other purchases easily?

I'd also like to set a cap or limit on purchases and apple warns me when purchases reach a certain limit. Is this possible?

My 9 year old son has and ipad mini and its attached to my credit card . He does check with me on purchases first and I trust him but Im afraid that within one of the many apps that require coins or purchases to get to a certain level he may not understand he is authorising the app to make purchases and is actually spending money.

For some other people this has meant large unexpected credit card bills which I want to avoid .

Thank you

Concerned Parent