I have never made a cranberry cider, but I have tasted one from a friend that was good. It will definitely give a beautiful pink color to the cider. You should be able to combine both juices up front, but could reserve the cranberry for the end of fermentation to save a little more of the subtle cranberry flavor. To keep things easy, personally I'd probably just ferment all together. I agree that 1:4 ratio seems good for this. The key thing to keep in mind:
Cranberry is extremely tart, and also tannic. This can be a good thing, especially if you enjoy a tart cider. However, you might want to plan on balancing via either a low attenuating yeast like Scottish or Irish ale, or employ my gelatin & chilling method to get rid of the yeast early, or backsweeten with plenty of xylitol, or a combination of all these things. Just know that it's going to be TART. You might also want to use low acid dessert apples on purpose for this cider -- Ambrosia springs to mind, and even Red Delicious (gasp!) might not be a bad option for this, since these apples are so insipidly without any acid in them. Don't use your Grannies for this one.
All that being said, I'd probably drink a lot of it no matter how tart it turns out.