I recently got a gate pass from Delta at MSP for our toddler and me to accompany papa to the gate (volcanic ash delays forced us to arrive ungodly early so we companionably hung out at the airport for a while). We had no problem at security.

At JFK, on the other hand, Delta *denied* a gate pass to my 14-year-old niece's brother (he was 21) who was supposed to escort her to the gate since she was flying as an unaccompanied minor. He had to leave her at security and didn't know enough how to be more assertive with the gate agent.

I was unable to get a gate pass at ORD to meet my partner and his two small children when they were arriving there from overseas, but that was several years ago now.