I have three children. My two boys have both been on Concerta. The first one went on it at 11 years old. It did not work for him. His ADD manifested itself in talking and not focusing. It didn't help. A very structured environment and elimination of virtually all pre-processed foods has been the key to getting him to function normally.
The second, now eight went on Concerta this past September. His ADHD manifests itself in not being able to sit in a chair for any length of time. He has done very well on this, although is having a bit of trouble settling down at night. We are in the process of implementing a very standard, set bedtime ritual to get him in the "groove", so bedtime isn't so troublesome.
I don't think any pediatrician is going to prescribe concerta to a toddler. Most pediatricians require a very expensive psychological evaluation before even considering any type of ADHD medication. You can find some out there to work with you without a psychologist, but they are difficult to find.
If this single dad was my friend, I would advise him to first set a pretty structured schedule for his toddler, then go about eliminating processed foods. Most toddlers love fresh fruit, so the sweet tooth should be satisfied with that, raisins, yogurt, things like that. Also, make sure the child is getting enough exercise during the day, and not being left to nap while dad is at work. I had a caregiver doing that once and I thought something was wrong too. My daughter was raring to go all evening, then I figured out the caregiver was letting her sleep 5 hours during the day. Grrrrr. Anyway, I digress.
If the child doesn't settle down after these types of changes, then I would definitely have him talk to his pediatrician about medication. But these are the same things pediatricians are going to tell him to do, before the consider meds. I've been there.