Toddler and Carry-ons

I’m flying out to Arizona with American and I’m confused about what to do with stuff for me and my toddler. I have a backpack I was hoping to have under the seat, but could I have something else for under my 3 year old’s seat too?

My husband suggested overhead storage, but wouldn’t it be annoying to constantly need to get in there for toys, snacks, and coloring books for the toddler?

I searched the sub and saw some posts where the toddler had to be able to carry their bag? He’s 3ft tall, and his backpack can barely hold Mr. Potato head in it. 🥺 is this true? Will they let me have two backpacks? Should I do a tote bag too? My purse is small small.

Our flights are 2hours-ish and then 4hours-ish. Thank you!