I only know about the Suzuki method, having started that way. You can google Suzuki teachers and find one in your area. I am not familiar with the O’Connor method. You should ask Michael about that. I would think 2 years might be too young but you could start with the 5 year old and see if the 2 year old shows any interest. You can probably rent an instrument and trade it up for a larger size as the child grows. I like the Suzuki method personally because they involve the parents and several of the parents of the kids in my group class learned to play violin along with their kids.