What to write in a graduation card for family member that was thrown out of HS but now getting GED Certificate?

OK, its my 17 yr old grandson who got expelled from his senior year for texting in class (4th warning) so he had to go to an alternative school to obtained a GED - which he accomplished and now the ceremony is tonite. I have purchased a money card and would like to write some encouraging words but because of some dissapointment in him not graduating with his senior class, I'm lost for I had bigger expectations but because of his attitude and some of his wrong choices ust left me with a somewhat bitter taste in my mouth. Also, early this yr, while in Vo-Tech school for Nursing, he dropped Nursing and decided he wanted to join the Marines. We suggested to him OK, if its the military then go into the Air Force, but he stated that he needed discipline. (I told him my foot up his azz would give him a taste) He's had a not so good attitude...deep down he is a lovely kid, no worries of drugs/alchohol. He thinks just because he will be 18 this year that he's a grown man and can make his own decisions...yeah, right, does he pay bills, Heck NO. Anyway, I am grateful and happy that he was to achieve his HS education. I will continue to support him, but he lost out in getting a car for graduation..