When our 11 week old is on her play-mat she stares at the various toys hanging down over her. It's so tempting to help her reach out to them, but is it a good idea to help, or is it something she should figure out in her own good time?
It shouldn't be necessary. To encourage babies to reach, you move or wiggle the object you want them to reach for.
At 11 weeks old, they may not want to reach at all, and just watching bright colours and shapes is ample stimulation, but you could try bringing objects really close, even touching the baby's cheek and see how they respond - either trying to grab, or turning the head.
Babies tend to get to all these sort of things when they get to them.
I have tried a few times to help my LO do something, like bang toys or move something from one hand to another. She never learned from that, she got to do those things on her own some time later.
I think that unless the child is willing to repeat what you are doing just by seeing it, it makes little sense to show her how to do it with her own limbs. She won't get it. Forcing anything isn't the best idea, I think.
I also see no real harm in doing so:) Make sure you don't do it too much and do it really gently. If you feel resistance, stop. If by any chance she smiles when you do it, and she doesn't seem confused or scared, why not?