I agree with the roman numerals, something simple maybe? Leave some space around it, and when they grow up get another tattoo around it with a symbol...
Congratulations! I second the idea about something to do with the date, or the year in roman numerals. Or maybe something symbolic of his name if he...
Welcome to cK! Wow some of those names brought back memories! But there's a reason why cK is still around - it's got the best community and the best...