If you were my mom you would want to get dropped off at the airport by at least 3:30 am.
But seriously, do you have elite status (can you use the special "elite access" line). Most times its not any better, but it also does not get god awful bad like the regular one can.
If you are elite, and are checking bags I would think 4:30 is fine, will leave you lots of extra time at the airport.