Fred was closing up the shop when the the patronus appeared. It took him a moment to recognize who's it was - but then the message sunk in and it didn't matter at all who had sent it (even if he had remembered it was Fleur's at about the same time the message had sunk in...)
He barely waited for the thing to go on to whoever else would get the call next before he was tearing upstairs to grab his brother. He practically shoved George into clothes, not really explaining what the rush was about, but it wasn't twenty minutes later before they were rushing through the doors at Mungo's - George now at least mostly informed.
The waiting room was less of a ghost town than most other wizarding venues had been recently, but he spotted Fleur right off. "Fleur!" He yelled, drawing attention and not caring as he and George hurdled a few tables to get to her. "How is he?"