I have a 40kW model and need to have it charged by 05:00 each morning. I have a 7.4 kW a.c. home charger which seems to deliver around 6.5 kW to the Leaf. Based on that, I put together the attached table which works reasonably OK (for me, anyway).
A more automatic and simpler way is to set the LEAF to finish charging about 1 - 1.5 housr *later* than you actually leave. In your case, the LEAF pack will end up about 7 - 8 kWh below a full charge. You can tweak it to your preference. You are the perfect candidate for this method