But do you recommend having more than one sim caring, because having only one seems daunting?
I don't recommend, the game practically imposes it; it's not dauting, it's the much more than that, like being a single mom of 6 (literally), but with less money. It's impossible to care of all the kids and keep the house clean and functional (your sim
will not have the silemons to hire maids and repairmen)
In the final level of the carrer there will be 6 kids, toddlers and children in any proportion, and if turns out to be 6 toddlers, your sim will, literally, pee in its pants, for there will be no time for such luxuries as toilets if it's alone.
But I understand that only one of them can have the profession or you might have double the kids...
The game doesn't allow for two sims of the same household to be in daycare profession, so there will never be double kids as you said.
Reminding: never, ever leave the problem child on its own!