My oldest daughter who is now 4 would also have a bit of hard time with change or new situations. I try to help her anticipate things by preparing her. For example, as part of her bedtime routine, we talk about what will be going on tomorrow and what she could expect as far as changes in schedule, new activities, etc.
When she is going to start a new class, I take her to it first, so that she could observe what is going on and be somewhat familiar with the new environment.
I also like a lot of the Berenstain Bear stories. They help prepare for new situations (like going to the Dentist or Doctor or upcoming holidays, etc.)
He sounds like a very sweet boy.