The waiting staff should get the money from the service charge. My OH gives less in tips if a service charge has already been added. The staff should get it.
Having said that, I've just come back from USA where, as we know, you have to tip almost everyone for everything. I find it really awkward. Do I really have to give a man a few dollars for hailing a taxi for me while there are loads of them waiting for passengers anyway? If you don't tip enough you get tuts and dirty looks.