iPhone question

I bought two used iPhones (6S) for my wife and me, and our 5SEs will be passed down to our kids. To set up the phones I simply do the following:

1. Back up phone to iTunes
   
   
2. Swap the SIM card
   
   
3. Restore phone from backup
   
   
4. Lather
   
   
5. Rinse
   
   
6. Repeat
   
   

Am I missing anything critical? One of the 6's is a Sprint phone, and all others are AT&T. I looked up the IMEID on the AT&T site and it said that it would work, so I don’t think I’ll have to unlock it.

Thanks; here’s an apple car for your time.