i cut for my girl If she moves too much, I'll break into part 1 and part 2, different days... stay home, never mind, she won't mind
When my son was young, I bought a set of hair cutting gear - with different 'teeth'. That time, was bath time cum barber time.
When you cut, be gentle, dont't let the 'teeth bite'/pull his hair (if too long, use scissors to trim). Use the 'teeth' to shape. No 'teeth' means 'monk style'. dont't use too long, some hair cutting equipment are warm and by touching his scalp, he may be angry.
For my girl, was either TV time or bath time.... till-date. have not't tried taking her out to be serviced by the professionals.
I forgot where I saw kid salon .... Suntec or United Square