Aw what absolutely super pics of your kids, Paula, and that young man of yours is such a poppet- he KNOWS he has a precious cargo on board. What a sweetheart. And just look at the position of your two little girls. In the first one, Grace could be rising with the upper body just a tad more forward, but what a way to start them off, on a saddle that allows their little bodies to go into the correct alignment without having to fight it.
When I go to riding schools, and see little kids already in a chair seat, because they are simply not strong enough to fight the saddle back, it pains me to see it, as I know just how they can ride on a saddle that assists them.
You are going to have two real naturals there! Your own position is overall very good, just need to get the knee deeper and heel down. Doesnt need to be more than half an inch lower than the toe for flatwork, so dont force it down, but move your knee rolls well back on the saddle and then do lots of work in walk without stirrups, and your toes pointing down- yes, down!! This helps to deepen the knee and thigh, and stretch it all there. Dont let your legs come forward so that you can see your toe when you glance down. Hold your toes down as if on ballet points for about 30 secs at a time, but not until you 'feel the burn' because then you are ripping, not stretching muscles!!
Guiness looks as if he is going very nicely, and looks such a happy chap too- congratulations on a job being done very well

!!
Heather