If you had some money & hadn't left it to the last minute,
The blue option is to use the car park as less tight chicane but you do need to tarmac it over
The Green option is to use the car park of the museum, but you need to create connections between the road and the car park - the main obstacle is a small ditch. Expensive, but less obtrusive.
The red option is to use the road thats closed outside the museum. Probably the most intrusive & expensive option - you do need to relay the road and do something about the museum gates.
Rue Lambrecht is only wide enough for a single rider.
This last minute fixing of problems is tougher than you think.