saying "Gram"

My mom chose "Gram" as her grandmother name and all 5 grand kids have had some trouble saying it.  The "gr" sound is difficult for most young kids.  She has always encouraged them to say it properly, and even offered a monetary incentive.  Aiden got his money when he said it when he was about 2 1/2.  Marley said it when she was 2 and was rewarded as well.  Ty has really been trying his best to say it, but instead of "Gram", what he actually says is "Dam".  He will call her from another room and yell it in almost 2 syllables; It comes out "Da-am"  When he sees a car like hers on the road, he'll say "Look, Dam car".  One time, he saw two cars that look like hers and he said, "Two Dam cars".  It is just impossible not to laugh when he talks about her and we constantly correct him, but it's just hilarious!