I know you're excited and want to order ASAP, but as someone in child care -- I would consider waiting. There are so many different factors and I own eight seats right now (for seven kids,) and none of them are duplicates -- partially to tailor them to the kids, and partially to fit them in my vehicle.
I don't know what you expect your situation to be, but I don't have very high turnover. I can usually finagle a seat when I get an enrollment, or can borrow mom and dad's for the first few days until I get the seat I want for the kids. My parents pay week-in-advance, so worst case scenario I take the first check I recieve from a family and use it to buy their seat. (BTW, it's OT but I would strongly suggest this if you haven't already considered it... that way you don't have a new family use you for a week and then disappear without payment.)
For babies, I've always found the easiest thing to do is have an extra base to whatever seat they end up using. So if the family uses a SR, you just need a SR base and the seat comes into and out of the house with the child.
If you really want to get some seats now, I would get a Scenera and a Maestro, then wait on the third to see who you get. EFTA might work well, too, for a seat to be shared between children, but it's wide and might not puzzle well with what you have. (Maybe, with the Radian in the second row...) Or wait and get an EFTA with the 40lb RF limit.
One other factor is (unless you have enrollments lined up) that you may not get enrollments right away, which leaves you out the money for the seats without the income to back it up. If Grandma is doing seats as a gift, then that's less of an issue, but if it's as a loan, that may be a problem.
The seats I've ended up with are in my sig. Yes, many of them are expensive seats to use "just" for daycare kids, but I also feel that I have an obligation to keep them *as safe as possible* in my vehicle. (That said, I use a Scenera four days a week and would love to have a Maestro, but I have no real reason to, lol.)