I wouldn't take on a family of three. I really not like to have two from same family but I would avoid 3. Not just because if they leave it's a lot of spaces to fill but also because some sibling groups and back each other to detriment of other children - power in numbers.
I really would not work with family who were previous employer. It complicated to switch from them calling shots, to you calling shots and them complying. Might start off good but old habit die hard and would be too easy for them think they are boss when they not.

I'd leave your great experience with this family in tact and look back with fun about that time. New chapter now, don't bring old baggage with you.