In my opinion they should all be the same machine. I think you are in for a big headache using several different ones for the kids to learn on. It would be too much confusion. Like another poster suggested I would have a fund raiser & ask for donations. My very first machine was a inexpensive Brother & I loved it for piecing. If you are trying to teach on several different machines it just wouldn't be fun unless everything went smoothly. This is only how I would want to do it but if it isn't possible to have the same machines then you will have to do what you have to do. Just have fun with the kids. Hopefully some will love quilting as much as we do.