Save up your coins and watch as many ads as you can prior to the event! I imagine many people will be watching ads while the event is going on, so watching ads in the days leading up to it can ensure you'll have coins in case you can't get any while the event is actually going.
And if you're speaking from the standpoint of getting tips, I'd let your readers know that the event is coming up, and tell them to save their coins until then. That can both help you gets tips during the event, and to just remind your readers to tip you in general!