Charles Helliwell's Answer:
The words 'children and train set' spring to mind, Alan. What you're dealing with here are individuals, whose only interest is self-interest. Consequently, your most effective approach will be to find a way to work with them on a level that they can equate to.
You've already established that they have no interest in the day-to-day running of a business which now employs 30 people; so don't attempt to engage them on that level.
It may well be that the three founders realise this, and this is why they hired you. You may well be losing your drive, energy and motivation, by trying to get the founders to take accountability for what they are now responsible for.
There's no point in pursuing this route, particularly since the business has now been acquired by a larger group. You are on a hiding to nothing. Put yourself behind the eyeballs of the founders and look at the business as they would now, as it is now. They are artists, creators and inventors; to them, the business is solely a means to an end, and now that they have struck lucky, they are thinking about their next invention and not the current one.
To them, the mundane aspects of managing day-to-day, are, as you describe, best dealt with in a two-line email or a thirty second conversation. Consequently, try and appeal to the one aspect of their circumstances which will directly affect them and what they do next; namely the earn-out they will achieve, as a result of the acquisition. You will find that it's extraordinary how quickly such a simple topic will suddenly focus their minds and attention.
In order to turnaround the current morale and operational issues and deal with the staff retention challenges, you will have to act as a surrogate general manager and take greater responsibility for the operational management of the business, without appearing to isolate the three founders.
This will require you to have a serious and grown-up conversation with the founders about what it is that you will expect of them, going forward.
Have this discussion out of the office in a neutral location. Prepare an agenda of what you want to discuss and what you want to achieve; and perhaps even include the services of a professional facilitator to help you. Money is a great motivator, and this is a great opportunity for you to grasp the mettle, Alan, and show the founders, the parent company and the employees, just what you're made of.