No ticket needed. I'd only be worried at the Astros games about the amount of sun depending on where you are sitting. We've taken Aidan, but we were in the suite so he could play and was in a/c so we didn't have to worry about him losing patience or getting too hot. I'm not sure I would have taken him this early without that.
I took Amelia many times last year to Astros games, they let you take them in under 2 without a ticket...so long as you don't want/need a seat for them. If you're club level there's a nice place to nurse her back by the restrooms on the first base side (it's quiet at that end of the hallway). If not then seek out the family restrooms, they usually have a seat in them. I can't WAIT to take Amelia to opening day again this year!
Re: Babies and sporting events