We leave next month for our first family cruise on NWCL Gem. Not sure if we should do the pre pay service charge or just tip as we go. Any recommendations? I know it's the economical way to go prepaying, but do you find yourself double tipping service workers this way. I know me, and I like to make sure my servers are tipped & may feel bad just walking away... How do they know you've already pre tipped. Any feedback would be helpful. Thank you.