No need to purchase in advance. These items (especially the autograph book & penny book) EVERYWHERE - all gift shops, even at the hotels.
Definitely do the autograph book. She can pick and choose when she wants autographs, if she doesn't want to approach each character.
Pennies were a great distraction for our two year old. When we wanted to move from one spot to another, we'd say, Hey, look over this way there might be a penny machine...and when we foudn one, it was amusing to puch buttons, etc. We bought the book once we collected a bunch of pennies. We didn't need it right away.
We used the passport, not so much for the stamps at each ocuntry, but becuase it comes with a bunch of stickers for each country's page...and two year olds love stickers! It might be over her head, as one poster mentioned, but she will still enjoy the stickers while she's waiting for her food to come at a restuarant. It's worth taking a peek at to consider if your DD might enjoy it.
And, absolutely have her do a mask at Epcot. They're great! There are 11 countries, and kids can add something at each country -- that might be a bit much for a wee one. Stop at a few and see what she's up for.
That's a perfect age for a trip! My first trip as a mom was with my first DD age 18 months (and I was several months pg). My second trip was with my DD 2 1/2 and DD 8 months, and my third trip was with my DD 4, DD 2, and DS 10 months. I can't wait to go again -- oldest DD will be 6, middle DD 4, and DS almost 3 -- and I can't wait to see his 2 year old face react to everything at WDW!!!
Enjoy!