Account Structure & Annual Convention

First of all, I'm a system administrator so I'll be struggling with some terminology. 

We have an annual Convention and my co-workers want to see our income and expenses for different categories of attendees and different activities (meals, childcare, registration fees). We also have to send invoices out for uncollected fees, of course. 

I don't know if it matters but sometimes a parent organization will pay for their representatives attending. 

In our budget structure, the Convention is already out to Variable 3, and the bookkeeper says she's pressed for account numbers for all the activities for Variable 4. 

We have meals for adults, meals for youth, meals for children, childcare, registration for adults, registration for youth. We may also have a spouse's category to track as well for meals and registration fees (though these technically should be reimbursed by another account). 

My coworker wants to see income and expense from these categories and compare from one year to another. 

Do we need to create a bunch of accounting variable 4's somehow, do we use line items somehow, or is there another solution? 

As I said, I'm not an Accountant (rather obviously by now), so thanks for hanging in there with me. 

Heather