Odds don't exist. Saving 5 people doesn't mean it's more likely that one of them will, say, save your life someday.
You can't even count on whether the families would be grateful. I think you need to put yourself in the place of everyone individually. If I was in one of the families, I'd obviously want my relative to live, so five of me means all five of those people would be missed, rather than just one.
On the other hand, running over five people would presumably derail the trolley, maybe killing/injuring people on board?
Also, if you ask me, not doing anything does not mean you didn't have a part in their deaths. And if you think nature should take its course, you should consider that you're a part of nature.
It's so complicated!
What I'd probably do is stand there and wonder about it until the trolley went ahead and ran everybody over.