Language / The names Julia and Dawid - tell me the nicknames for these 2 names? [4]

The names Julia and Dawid, they are two polish kids who go the school i help at. They are so cute (twins), they only just moved here and I would like to talk to them and adress them in a way that makes them feel at home!

i know that polish language does have like a system for nicknames and diminutives but i don't know what it is! But any nicknames you give me for these names would be great.

Thank you!!!