Hi Shelly....your boys are really pretty!
As far as the saddle....keep in mind the 12" measurement is just the size of the seat...its a measurement used for the rider...not the fit to the horse. They do make a smaller seat than 12" if you need one, most mini tack dealers have them.
Basically, you need to measure the horses back (length from about the end of the mane to the start of his hips). A saddle that is too long will ride up on his hips and not fit right. Also do a girth measurement.....use a soft measuring tape, measure around the barrel of the horse...to make sure the girth of the saddle will fit around him so it can be cinched up. They do make several sizes of girths that can help fit a saddle.
Some pony saddles will be too large...so just have to have some of these measurements handy to know if it'll possibly work for your boys.
Have fun!
Connie