Those are so cute!!
I would border the blocks with solid fabric in that muted blue. That will distance the blocks a bit from the busy (but adorable) snowman fabric. Your sashing is limited to what you have, so if you also cornerstone the sashing with the muted blue, you can still use it. If your blocks end up slightly different sizes after you square them, make the blue different widths so they all end up the same size.
Wonderful that you are finishing this delightful piece!
hahahah! bkay & I cross posted. It must be a good idea if we both had it. hehehhe!