About all I can suggest is that you keep them away from him as much as possible. You don’t say what the family business is, but I’m guessing it is a small store. Try to set aside a play space for your children that is as far away from where he is likely to be as you can manage.
Your question makes me very sad, as I have worked all my professional life to educate the public in general and politicians in particular about the need for public funding of quality child care for all our families that need it. We still have a long way to go. But perhaps in your situation there is a middle ground.
Could you afford to enroll your children in an early childhood program part-time and keep them with you at work the rest of the time? If you are working, you can’t possibly do with and for them the things that children their age need (reading stories, singing, playing games, using toys, doing art projects) and I hate to think of two such young children having to fend for themselves all day while you work. Put on your creativity cap and see what you can work out that would be better for all concerned.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.