In my opinion, you should at least put them in first team and use them several time in subs. This will guarantee you the positive progress of your young star players.
For another option, you can loan them out, but basically it will not turn out so good and sometimes quite waste of time.
about the thought of putting them in the reserve. Actually I put them in the first team but sometimes let them play in reserves. Try to mix them in subs for first team and when not used put them in reserves. I think that would be better.