Let’s see how discussions go in this community
… “Second problem: You’re underage, which means you’ve still got the Trace on you.”
“I don’t —”
“The Trace, the Trace!” said Mad-Eye impatiently. “The charm that detects magical activity around under-seventeens, the way the Ministry finds out about underage magic! If you, or anyone around you, casts a spell to get you out of here, Thicknesse is going to know about it, and so will the Death Eaters." …
Should not be a problem with proper planning. Assuming the Trace tracks side along apparition and shows the destination, just have another mode of transport waiting at the destination.
Apparition -> broomstick -> knight bus would be a simple chain to set up.
Alternatively, depending on the exact mechanics of the trace, multiple apparitions from the same spot could be confusing as well, possibly even in addition to the poly juice plan.
If the trace does not record the identity of the underage wizard that’s causing the alert, adding more underage wizards to the equation would cause total mayhem, especially given the usual “competence” of the ministry.
Depending on how cunning you get, using an information channel you control to feed the opposition false information should be possible as well. Set up a plan requiring specific spells, cast them near “traced” Harry and walk the opposite direction.