The YA Book Club discussion

I was thinking something along the lines of:
5 children are chosen to take part in an experiment, to be frozen in time. They go in 2020 and come out 2040?
3 children survive, and it is about how the world has changed. There are new diseases that threaten the human population, as well as creatures.
I don't know. This is me sitting in my bed thinking of random stuff...

... Random stuff...

I love Sci Fi books, and it does sound interesting.
Just do some research first and try to read some classic Sci Fi, and since you are talking of kids, read some young adult or middle school sci fi too, just so you don't write a similar story without knowing it.