Are helpers nowdays more choosy? Refused to help employers with more than 2 kids?

I think they are "choosy" because they are worried about not being to manage and cope well if there are too many children and household duties. If they don't do well at their job, they risk being replaced or sent back so their livelihoods could be in jeopardy. Talk to the agency you're engaging and let them know your household and family needs -- usually they will try to match the family with a helper that is much more experienced if it's a bigger family.