Different Apple ID for every member of family

Me, wife, and son have iPhones, but we're all 'logged' in with my Apple ID.

I was wanting to set them up with their own Apple ID's so they can have their own contacts, etc. and not be stuck with my contacts and data. But I'm concerned that their current data (that's currently on their phones and iPads) will be erased if they 'log' on with their new Apple ID's.

I'm also concerned that they will no longer have access to the apps I have purchased under my Apple ID.

I am generally very "Apple-savy" (very computer savy too) but this issue really confuses me.

Can you guide me on how to set up distinct ID's for other members of my family and let me know about the concerns I have. Or reply with a link that has instructions.

Thanks.