Unless you are taking true babies as in 10 months and under you would be surprised at how independent and self sufficient they can be or could become very quickly. It doesn't matter if they use fingers or a spoon it still takes the same amount of time to cook noodles and serve to 3 or 6. As far as diaper changes go you get very quick at it and in reality I can change all in diapers faster than I can potty train a couple older ones. They will be fine playing on the floor, crawling around with a few toys while you change each one in succession as in do not feel that you must be right there with each child all the time. That truly does the child a disservice on growing up independent.

If you have an assistant lined up then that is good. Your provincial office will have info on how to treat them from an employer-employee standpoint.

If you are concerned about the age mix and work load consider starting with the three little ones and then as they grow a bit (self feed, walk, etc) then add another baby so that eventually you are up to your maximum allowable number of kids but by then you will have the ages spread out so some are one and some are closing in on three. That is pretty much what happens with me in the sense that as kids leave to start school I start new babies in their place and my middle group becomes the big kids and this process happens on a yearly basis pretty much. School in Ontario starts with JK when they are turning 4 so for us all kids are aged 1-3 in our daycares unless we take school age.