If you can guarantee that you will stay together the entire trip, only one
DAS would be needed. But if there is any chance you will split, then get one for each child. You can only be listed on one active DAS at a time though, I think? I'm not wording it correctly - someone with the right words, feel free to help
Also, you aren't guaranteed to 'fit the criteria' unless the CM at Guest Services thinks so - just have a clear, logical explanation why your children cannot handle a standard queue, and why waiting in an alternate location would help.