Corresponding with family in Poland

I've been writing to family in Poland for a few years-mine are in English' their's are in Polish. I can usually understand most of the letter but because the penmanship is so different, I'm not always sure. How can I ask an older cousin (wujek)to print his letters without insulting him. I also have problems with case endings for the greetings. How do I correctly say " dear Uncle Stanislaw (or Czeslaw) and Aunt Jadwiga (or Krysyna)? Thanks for any help.

Drogi wujku Stanislawie (Czeslawie)
Droga ciociu Jadwigo (Krystyno)

Dziekuje bardzo, Bunia.

Im sure you can :) If you ask politely it wont be taken wrong.
But before you do - make sure he has an easy access to computer or some1 who will help him type fast :) It might be a bit frustraiting to him :) (it took me ages to teach my mum using emails and she types really slow :)

You could say something like that:
Drogi wujku, poniewaz moj polski nie jest doskonaly czasem mam problemy z odczytaniem waszych listow. Czy moglbys pisac je na komputerze? Moglabym wtedy uzyc elektronicznego tlumacza, zeby mi pomoc je zrozumiec i polepszyc moj polski.
Dziekuje :)
Which is translated:
Dear Uncle, because my polish is not so great ive been having problems with reading some of your letters. Could you please use computer to type them ? I could then use electronic translator to help me understand them and improve my english
thank you

Hope it helps a bit :)

Thank you again for your help. I know that wujek does not have access to a computer so I would ask him to print by hand rather than use cursive handwriting. His niece, my 19 yr old cousin Monika has a computer & has been translating our letters but he prefers to write by hand.