Santa:
Splitting it might be a good idea. If you take it all at once it will put you into the 40% rate for that week.
Not unless he’s earned into the 40% rate for the previous 40 odd weeks of this year. You don’t get put into the 40% rate just because you earn over £800 odd quid in a few weeks. You need to have been near the weekly level for pretty much every week up to that week to have that happen and even then if you’re not near it in the following week the tax will rebalance.