You have asked for honest opinions from people of experience. Here is mine-- I would not breed either the silver(grey)or the palomino. Although I do not think that the silver could be classified as a dwarf, in my opinion, she does have some conformational features that may well be what I would call "indicators" of dwarfism-as others have said, the oversized belly(which IS one of the characterisics that indicate dwarfism; sometimes part of a syndrome where the intestines(and often, the genitalia, on stallions, especially) are 'too big for'-in other words, not proportionate to- the horse. I am also concerned,on the silver mare, by the VERY short limbs, with coarse, heavy bone structure, the overlong torso, and to a degree, the still-quite-evident forehead bulge. The other mare shares the overlong torso and over-short legs. Even if these are not taken as evidence of minimal expression of dwarf characteristics,I believe that horses of this type of conformation do not fit the accepted standards of excellence in conformational features, and honestly, their offspring would likely be hard to sell for any sort of decent price-AND, would be very unlikely to contribute to the betterment of the miniature horse breed. Also, increasingly, miniatures who sell only at very low prices(if at all)are too often are not really highly regarded by their purchasers, so too often end up neglected and/or cast off or going to killer auctions--very sad, but it is happening.
I must also add that there is NO WAY that I, personally(with 22 years experience in breeding miniatures, and 55 years of using, training, AND breeding horses)would breed ANY 26" mare, even is she were of excellent conformation! I consider it far too risky for the life/health of both mare and possible foal,so I just wouldn't even try it.
Both mares look sweet-natured; I can easily visualize you enjoying them as dear pets!
Margo