I'd add a mini mole wrench (with lessons if necessary) and explain how much
easier cross-point screws are than slotted. Given the amount of stuff held
together with allen keys, perhaps a set of them (e.g. the Screwfix ball end
ones). Oh, and plumbers two part epoxy sticks. And some rolls of PVC tape.
Araldite. PVA adhesive if they are going to do any decorating. And a
stud/wire detector if they go for the drill and masonry bits.