Do I need to purchase a ticket for my 2 year old for a baseball game here?

Well anyone over 24 months needs a ticket. But you can just said he is 20 months old. But he would have to sit on your lap. Strollers are allowed to get in. But once on your seat it has to be folded under your seat/s.

Child under 24 months does not require a ticket but must sit in someone's lap. They are not assigned a seat.

They answer you question