Should I tell my boss before she arrives at the office?

I work for a VERY small company owned by a married couple. There are 5 of us workers. Our team leader wants to make a "fake" time sheet to fool our boss as an April Fool's joke. Her plan is to make our boss think we all arrived long after our shift start time of 8am....she (team leader) arriving at 10am and the rest of us arriving between 9:30-9:45 which she thinks will confuse the boss since the team leader is the only other one with keys to the office. I think her idea is a bit mean since she's not doing it in fun as a joke but to make our boss look stupid and ignorant. I'm torn between texting my boss in the morning to warn her (she typically doesn't answer her phone) or keeping my mouth shut. The 5 of us coworkers work well together and I don't want to spoil it but at the same time I can't afford to lose my job should my boss take the joke the wrong way and fire me as an example. Should I tell or keep quiet?