Hello :)
The best thing to do when introducing a new kitten/cat into the home is to provide a small safe room, where they will have everything they need (water, food, litter etc). That way, they are able to get comfortable on their own (away from grabbing hands and loud noises) and if you frequently visit / sit with them quietly, they will eventually become curious and happy enough to venture out.
If you can still provide that for her, it would be best. But if you feel its too late, or just cannot provide her own space.. you will just have to wait. I'm not sure how old your kids are, but let them know she needs time to adjust and ask them to not grab at her etc. I guess it could take anywhere from couple of days to a week, depending.
Just curious, what country do you live in? I don't mean to offend (as you said, you got her from a friend and she was already declawed) but I'm curious as declawing is seen as very inhumane and illegal in a lot of countries. To be honest, it is quite disappointing to hear that it still happens
Cats need their claws for climbing, defence etc, I don't think a declawed cat will do very well outside on their own.
I'm not sure what your plans are, but in my opinion (and again, I'm not trying to be mean or make you feel bad) she should be a strictly indoor cat with supervised outside time/walks etc.
All the best with the new addition
Keets