DH booked our flights but I have just realised that he put an abreviation of DS's name It is what we call him but it doesn't match his passport. Have never flown with Ryanair before but have heard they are really pinickety about things. Are they likely to refuse him onto the flight do you think??
It will depend entirely upon how aresy the staff choose to get. I have been accepted with an obvious abbreviation of my name, and on another occasion turned away because I couldn't spell my own last name. (It was a typo but there you go...!) Contact the airline and ask in advance - it will be cheaper (probably) to change the name than to lose the whole holiday.