The root system is huge, so the trees are going to have to adapt to whatever your native soil is. Unless you have a lot of funds and access to a backhoe, you aren't going to modify a large enough area for them.

I might add some course sand or decomposed granite to as large an area as I could stand to dig.

If you get a lot of rain, you might resign yourself to spreading a large sheet of plastic mulch around the base of the tree every time that there is a heavy rain. If the soil won't drain, you can't do much about the soil, but you can have a bit of control over how much water goes into the soil. How badly do you want cherries? Enough to do extra work to care for the trees?

Don't ammend. The trees would end up in 'pots' of nice soil surrounded by clay and wouldn't be at all happy. Clay isn't all bad, it holds water well so you don't need to water very often. You will need a good mulch on the surface. No fertilizers either until you have a soil test. Trees don't need much for fertilizer.

One good piece of advice - check the roots carefully when you plant those trees. You'll want to dig wide rather than deep and try to spread out the roots when you plant. This is much easier with a bareroot tree as potted trees tend to be rootbound and stuck in their pots for way too long.

Both of you have pretty much said what I thought too. I've heard stories about how people ammend a small area and then the tree's roots don't develop well outside the ammended area; when a bad storm comes along once the tree has some size to it, they end up falling over. So my inclination was not to ammend very much. I was thinking just a bit of sand and some composted manure, but nothing major. The backhoe has got me thinking though. I might actually be able to pull that off... It would also be a heck of a lot easier than trying to dig a hole in my rocky clay soil. The last time I had to dig a large hole in my yard (for a small pond) it took us THREE days of hard labor because the rocks are so bad. I felt like I was in a prison camp. LOL!

I was just wondering what other conclusions people had come to. I appreciate your comments folks... I was doubting myself and it helps to be reassured.

If drainage is poor, consider growing on berns. Even with a shovel it is not too hard to raise the soil an adequate amount to create better drainage. You could also bring in abut 3 yards per tree of a courser soil to create adequate mounds to grow a good sized tree. Roots will also work the clay and trees will probably anchor quite well this way.

athenainwi got it right about "pot" holes. just back fill with native soil. and most "clay" soils are not as bad as all that, and are not pure clay but a mix of clay and loam.
Just add a good bit of mulch, starting a couple of inches away from the trunk and extending out 3 to 4 feet from the tree all around. Start with mulch 4 inches thick and top dress it back to 4 inches any time it gets to less than 2 inches. In a year, your soil will start to develop the same natural horizons a forest soil develops and your trees will adjust to the soil layers.
remember, it's a tree, not a squash, so it takes time to develop into a nice strong tree. The first year, pull off any fruit that tries to set, and I recomend the same the second year too.