The two are practically inseparable and we have what seems like an unsolvable dilemma: we want to allow the 7yr old to watch, for example, Star Wars but feel it's not adequate for a 5yr old. How should we proceed?
Arrange something like a playdate for your 5yo or one of you the 5yo somewhere so that the 7yo can watch the film. Do something like explain it way as separate treats.
Also gently explain rating systems and put in terms they understand like little children, big children, teens and grownups and its there so you don't see something scary/yucky.
With my kids, most times I went down the route Ourjamie mentioned - it's very effective.
As I have two separated by 2 years, and a third 4 years younger, sometimes my youngest did feel a bit excluded by this so at that sort of age we sometimes would all sit down to watch the film, including the youngest, but provide her with some toys and colouring books, and the opportunity to cuddle in and fall asleep if she got to bored.
At that age, their attention span is not great anyway, so while they may love the intro with all the explosions and lasers, they are likely to get bored after that once the plot starts to become evident, and getting them to draw a picture can be a wonderful distraction.
In reality, I don't think there is much in there that would be negative for a 5 year old - it is a franchise with very little death (if we exclude whole planets being destroyed, I guess...) and some nice obvious heroes and villains that will be understandable even to a 5 year old.