[x] Frame it as a way to build camaraderie among the officers of the Home Guard
First choice, because that was my plan all along.
Second choice, because kicking out Albion's guests (which are mainly there to build a better relationship with Magical Britain) will not look good. It's like Albion is trying to requisition a building which was lent for the ambassadors to use as they please (when Shinji and George could have used the HQ grounds to train). I get that people want privacy but I don't think the repercussions are worth the risk.
You're basically sabotaging the public reputation of Albion for the sake of a spar with a colleague.
Shinji was technically put on Homeguard duty in order to restore his reputation too, not the opposite. We don't need more people angry at him, and certainly not those whom we work for and those we risk our lives with.
If you guys want to go for a write-in on the second, please keep what I mentioned in mind.
EDIT: after discussing the second choice on discord and getting the green light for a write-in from Alf;
[x] Ask the guests if it would be acceptable for the Homeguard leaders to borrow the training ground for some private sparring and apologize for the inconvenience it would cause in advance. If the place is already in use, the two of them don't mind waiting and observing - if allowed - or scheduling a spot for later.