I have always wanted a Morgan! She's beautiful.
I agree saddle 3 is the best fitting of the three. The first two are too narrow.
I also agree the third one may be a little wide with a rider in the saddle, but it's better than the other two. You can see that the seat is level when it's on her back. The other two, the seat tilts backwards.
You can look up saddle fitting online and learn how to "trace" her whithers, and then bring that with you to the store. I would also bring the pics and saddle #3. And of course buy from a place with easy returns!
YOu could also consier a saddle with a changeable gullet (collegiate makes one, pessoa I think makes one, and Bates). I have the Collegiate, and I'm very happy with it. I also saw recently in Dover saddlery catalogue, one of the saddle makers has a whole new line of wide saddle with changeable plates. Might be something for you to look at too.
Have fun! I'm a post children returning to rider, too, and I LOVE it!