He says the couple could holiday separately (which is not ideal for their marriage) or close the doors while they take a break (which is not ideal from a cashflow perspective but is the most common choice made by firms in this situation). Or they could find a temporary manager to take over in their absence: "But there are not many of these around."
He says they could get their external book-keeping contractors to manage the administration and accounts in their absence and direct the staff via the internet. Clear instructions should be left and staff should know how to get in touch with them.
Most businesses will be able to survive for a short period of time, even if the idea of leaving staff to it makes owners uncomfortable. More advice for owners: delegate a bit more of the workload to staff while you are there so there is a spread of knowledge. Let your major customers know you're away - if they know how hard you work, they will probably appreciate that you need a break.
Invest in staff training to help them work independently.