I'd go with a Kindle fire. There are interactive books that your children will like, plus Amazon has Free Time Unlimited which for a monthly fee allows you to access lots of books, movies, & games that are kid friendly. You can learn more about it here:
https://www.amazon.com/gp/feature.ht...cId=1000863021
Be sure and get a good case for it. The 8.9" models are on sale, starting at $269.