hi my son is 2y 7months and i have used a shaver on him for about a year now the only problem i have found is that he will not have his hair cut at all now
my son was 12 months old when i started shaving his head. Now at 16months he loves having it done as he sees daddy doing his hair too. The only thing I struggle with is the nape of his neck. He doen't want to look at the floor so I can get to it.
My sister is a hair stylist and has cut both of my boys hair since they could sit in the chair at the salon. Just be carful who you have to cut their hair. if they have even one bad experiance they may never sit well for a haircut again. Make it fun for them. And reward them if they sit well and behave for the person who cuts their hair.