We (2 adults, a 5 year old and a 3 year old) are thinking of taking the Caledonian Sleeper from London to Inverness. We thought we might be able to get a single cabin with 2 berths, and share them (1 adult and 1 child in each berth). We're fairly used to sharing with the kids, but: (a) is this allowed? and (b) are the berths big enough? We've shared berths on ferries before without any trouble, but if the sleeper berths are really tiny we might struggle.