The Eagles could come.
More seriously though... the sewers have been shot down because of over-use and sheer difficulty.
We could do the hiding-in-plain-view approach, but that already failed where the King's Men didn't believe that the group was another bunch of them.
Our idea needs to be creative, clever, and unused (which means those darned Eagles need to stay put).
I'd say it would be better to avoid being overtly sneaky, but not to be too obvious. Is there a place in the city that these three would have reason to go? Once they're in the city, we can work from there. It's just getting them in without getting them in prison.