Assuming this is cotton fabric, I would fill a small basin with cool temperature water and put some Tide in it. Then I would soak the blocks, sorting them by red background, black background, etc., the best you can. I would soak them for about a half hour and then run cold water over each block to rinse the blocks. I would dry the blocks on a towel (the right side should face the towel and the back side should be up). I probably would press the blocks from the back side very lightly on a towel before piecing them together, but that is a judgment call you should make after soaking the blocks. Before doing any of this: 1) do one block only as a test; 2) if you see find you want to do this with all the blocks, I would probably only do five blocks at a time in each small basin of soaking water. You want to keep a clean and odor free basin of water. I think you have some beautiful blocks and the history of how you got them and putting the quilt together is what will impress people for years to come. As a side note, you probably just made every quilter on this Board with UFO’s feel like a million dollars telling us about the blocks you inherited. As far as designing the quilt, anything you do will be fine.