What is that supposed to cover though?
Just "discretionary" fun stuff every month?
Or things like annual bills, car running and repairs, annual insurances (house, car, life, travel, health, any others?), buying clothes (for DC and yourselves), cost of afterschool clubs/hobbies etc, sports equipment...which are not necessarily needed every month but are generally part of the annual budget.
What about holidays and gifts? Day trips or outings for yourselves? Birthdays, Christmas, other celebrations (Christenings, Weddings, Hallowe'en, Thanksgiving, Hannukkah (sp?), Eid, ….your own special family days)?
Have you thought ahead for education for DCs - secondary, Uni, etc?
Have you a nest egg for emergencies, of at least 6 months of your annual budgetary needs (preferably a year)?
What about replacing a car in a couple of years, or boiler repairs, or "I feel like redecorating the living room" types of non-typical expenses? Have you money put aside for these things?
The notion of a nice chunk of disposable income on a monthly basis sounds good, but it really does depend on what you both think it is supposed to cover, or how else you are going to cover the various aspects of life.
So you and DH sound like you need to sit down and work out what you think falls within the category of "discretionary", and if you have actually covered off all of the general expenses of your individual household, and also have a safety net of emergency funds available somewhere.
And that should point in a much clearer way towards whether you have enough to live on comfortably or whether you need to rethink your plans following that life-changing circumstance - you may need to have some way to earn a small amount of money on an ongoing basis for security, but a couple of hours a week or something that is a short seasonal thing perhaps rather than 2 FT jobs. Or put some funds into secure investments that will give a guaranteed income, whatever about other investments.
It may even be an opportunity to think about doing something completely different - doing training over a period of time to move into something completely different and less stressful or fits better with family life (see above about potentially PT or seasonal/short blocks type money earning), or may be far lower earnings but enough to cover what you need and much more enjoyable to the person doing it than their current role. But you might have a chance to make changes now that would allow that different earning in a year/few years when needed.