For your cruise for two of your the total gratuities is 109.20 GBP. You can have these added to your holday cost with your travel agent and pre-pay them (check they weren't included in the price anyway). If not you can simply have them added to your on board bill of package up dollars to the equivilant and recommended amount at the end of the cruise. If you pre pay they basically deliver vouchers and envelopes to your stateroom for waiter, asst waiter, head waiter and cabin steward already broken down into the recommended amount the last but one night I think. You just hand them out at the last meal and leave the cabin stewards in the cabin. When we were on the legend of the seas we even topped these up with extra cash due to the fantiastic serviced. Oh and don't lget the Brilliance of the seas stuck in that canal we need it back at Southampton for our next cruise in May.
Gratuities for that cruise are £54.60pp. Most T/As will quote the price including this so check with them to see if you have already pre paid.