In setting-up the iPad from your iPhone, the iPad will be using your own AppleID - and will have unfettered access to all of your personal and sensitive information. This is certainly not a good idea if you intend the iPad to be used by anyone else.
Your child should have their own AppleID - in fact, every user should have their own AppleID. This is essential to maintain intended separation of activities and to avoid unintended sharing of unintended information and data. The iPad will need to be fully reset - before it is set up again:
What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support
You may find this information to be helpful with setting-up an AppleID for a minor - and in considering appropriate controls while continuing to share Apps and paid Apple services if you should choose to do so:
Apple for Kids - Official Apple Support
Help your child set up an iPhone, iPad, or iPod touch - Apple Support
Family Sharing and Apple ID for your child – Apple Support
Use parental controls on your child's iPhone, iPad and iPod touch – Apple Support