I have a new ipad up and running. Can I refresh the old one without affecting the new one?

BigTerpFan wrote:

We have a new ipad that is up and running. I want to clear out everything from the old one to give it to our grandchildren. If I refresh or delete files will it affect the new ipad?

Yes do this to your old ipad What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

If you correctly prepare the iPad for a new user, you will not impact your other devices. The simplest method of preparing the iPad is to follow this process:

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

This procedure will erase all existing data and sensitive information from the device - and, essentially, remove the Activation Lock that will otherwise inhibit reuse of the iPad.

Be aware that manual deletion of data may indeed cause loss of data on your other devices; changes/deletions may be synchronised via iCloud.