Easter weekend is arguably the best weekend to do something like this. It's not an actual holiday, so there are none of the normal precautions taken around bank holidays (bank vaults tend to have a lot of the money moved out around bank holidays), but much of your staff (and external forces, like cops) will be away outright or preoccupied.

It makes the entire thing far more seamless, and gives you a better window to get away with it.