Do it right when you board the ship. That was our plan in Nov (to use Rewards Points) and we didn't go down until the 3rd day. We had already gone over $500 on our on board account b/c of the tips so they automatically charged our credit card on account. And I will say the feedback was NOT positive on our cruise!
This happened to us last week also but we still applied our gift cards and got a credit to our cc. I was sure to ask at GC first just in case they decide to refund the OBC back to my TA or something. GC confirmed that my cc would be first to be refunded but we agreed that should wait until the last night once all new charges are posted. I knew we'd have more since we were doing Onboard Check in and our luggage fees for our return flight would be billed to our account.
Personally, I don't mind the new policy. It will save me the effort of dealing with filling out that form and going to GS. In 10 DCL cruises I've never felt any tipped position deserved less than suggested amount. Sometimes we give more, sometimes just the recommended amount. There are plenty of times that we passed by GS and there was no line at all so anyone who prefers to pay cash, my parents included, would just straighten it all out at their convenience.
Also in Apr we had non-family in our cabin. (Long story short, we traded kids with a friend to give them our dummy date but had to keep 1 original guest on that res so we put her son in with us, and our son with them.) It was easy at online check in from home, to designate who was responsible for which child's bill and which credit card would pay each tab. No problems at all and both kids had charging privileges and excursions billed to their accounts.
It only got hairy since this was the 1st time I prepaid tips and wasn't sure how that would work. Our friends didn't so we weren't sure if I prepaid for my son or her's and if my son in her cabin would get billed when she adds her tips onto her account. It all worked out fine; my TA had them prepay tips for my own family including my son in our friends cabin.
Anyway, none of these minor technicalities would make me cancel my cruises or leave DCL for another line. I can't deal with the drinkers & smokers on other lines.
I'd rather just go to work.
JMHO.
It would be nice if they could announce any and all changes 1.5-2 yrs in advance which is the approximate timing of when I book our cruises but in reality it just doesn't work that way.
Considering that the hospital I've worked at almost 22 yrs just decided to cut our annual # of sick days from 12 down to 5 with less than 2 months notice, I have learned that's just how life is sometimes and you just have to roll with it.
Of course there's always the option to have a fit and walk away.