Everything is stacked or nothing is stacked. Since folders are not stacked, you can put those two files inside a custom named folder (e.g. Special_Files) on the Desktop. You then drag and drop that folder onto the Dock just to the left of the Trash.

Now, right-click on that Dock icon and choose View Content as Grid. When you click on that Special_Files folder in the Dock, you will see per my example:

When you pass the pointer over the document icon, press the spacebar to open it in Quick Look. No need to click on the icon. If you do single-click the document, it will open in its default opening application.