Updates and credit card info Please help

I have a itunes account I got an update tonite on my ipad for ebay usually when I click update it will ask me for my password which I love because I have a iphone, ipod that is my 7 yr olds as well on the same account and when they ask I ca nrest assure its something I want to pay for cause to a 7 yr old .99 and 9.99 are the same..tonite it didn't ask for my password. I want to ensure my 7 yr old can't go on a buying spree..lol how can I check this out. Please help. Thank you