I have 3 years old and I want to know if I to buy a tiket for her?

Children who are 3 years old and younger and less than 30 inches tall do not need a ticket for entry; however, the child must sit on an adult's lap during the game or match without obstructing the view of other Guests. This policy may vary for other events.

I'm not quite sure as I bought tickets online for two people but I think most major league parks they let you have a baby coming in for free under the age of maybe three

Yes

Check their website to see if they need a ticket as well

Yes 3 amd under do not need a ticket as ling as they are sitting on your lap. If they need a seat for themselves they need a ticket

If she sits onbyour lap, no ticket. If she uses a seat, you need a ticket