C5 will definitely be too light for you by the summer if you get into the NC40s. C5 is more like an NC 35ish shade, just with more yellow in it.
You would love Face & Body during the summer! It is basically a long wearing tinted moisturizer that is meant to even out skin tones, as well as leave an almost glistening glow to the skin. As the name implies, it can be used anywhere on the face and body and is perfect for photography and an ideal makeup for people that like something light and natural looking.
It can also be used along with any other makeup such as concealors, powders, bronzers, blushes, etc. It can also be layered with other foundations, but I would personally finish with this product because of the healthy-glow finish.
The only thing I would suggest is to use a moisturizer that contains SPF in it if you're going to be wearing this during the summer. Face & Body Foundation does NOT contain SPF so you will have to use a seperate product to help protect the skin from the sun and elements.
Hope that helps!