One thing I always do with my kids is go to customer relations and get a free pack of baseball cards. If we are sitting in the Terrace, can go to customer relations up there and get a pack as well.
If you pay for parking go the the designated driver booth to the left of the main entrance to get a free soda voucher.
You used to be able to bring pretty much any food into the ballpark but more restrictive now. Can bring an unopened bottle of water/soda for each person plus a snack (peanuts, licorice, chips etc.) for each person.
Agree with T that the food inside is bad, the price is understandable because that is ballpark prices but not paying for expensive and bad. I do like the fresh popcorn on the main level by the entrance.
The Bud Selig Experience on the Loge level beyond Left Field is good if you have never seen before, hasn't been updated though. Is free, about 15 minutes or so and some memorabilia to look at after the video is done.