Oh yes, this annoys me too!! I get my older child to help me get the little ones ready and then she gets ready with me. I make the children who are done sit in front of my fridge while they are waiting. I ask what they want to sing and we sing tons of different ones until we are ready. I have also given them books to read while they wait. Other times it's just a stern "you are ready. sit here until the rest are ready"

Summer, Fall and Spring I get the kids ready 1 at a time (they put on what they can in the meantime) but in the Winter I will usually get everyone's ski pants, boots, mitts, toques on and then I put everyone's jackets on. This helps with the first ones getting too hot while they are waiting.