It isn't necessary, but there is somewhat better acceptance without the attendants. I've done both successfully. Having 10 thumbs personally I'd leave them.
When placing the queen, place the cage by some of the bees in the hive, and see how they react. What you will probably see is the bees walking calmly over the cage in communication with the queen. If they react more violently(biteing), then you may want to remove the attendants and spray with some sugar water with honeybhealthy or a scent.
But with a split and queenless for a day it usually isn't an issue.
If you wish to remove the attendants, the two way that i've heard is
1. in a bathroom with a small window, they will fly for the window an that is where the queen will be if she escapes
2. in your bee veil so she can't fly away.
-rick