Two accounts one one iPod Touch and Computer

Here is the setup that i want and want to know if it is possiable and if so how. So my parents have the iTunes account password and the reason that they will not tell me is becuase there is a credit card tied to it and don't want to to spend more than i need (even though we only use gift cards), so i see where they are coming from, and i agree with them. So my idea is to have two accounts. The main account, which holds all of the media that we bought, like music movies and apps, and then make another iTunes account for the iPod Touch that i will know the password to and can get free apps and put my own gift cards on so i will have my own 'gift card money' and becuase i won't enter a credit card on this account i cannot overspend more than my gift card has. The only catch is when i sync it back to my iMac which has all the iPod's/iPad is connected to and the family accounted synced to it wilcan i authrize the computer to be with 'my' account so that it will show u[p as able to by synced and that teh free and paid apps that i buy with mu money wil be able to be authorized to be played or used with the family account so everyone can use the content i buy?