When Jack and William Maguire-Wright were 2, their mom, Jennifer, introduced them to a PBS drawing app. It was a creative activity they could enjoy together, and they loved being able to paint with their fingers "before they were even able to hold a crayon," Maguire-Wright of Mount Airy said. "The intent was to be able to interact with them using technology while still getting human feedback."

Now 4, the boys can navigate some apps on their own - like finding their favorite show on Netflix or using the Endless Reader literacy app. But their parents still enjoy using apps with them, Pokémon Go being a current favorite. "We've been catching Pokémon as a family. We'll find something and take turns throwing the pokeballs at it," she said.

The twins still prefer playing with trains and dinosaurs, but as members of the 70 percent of U.S. households with children who have tablets, according to a wireless-communications industry advocate, their iPads are a big part of the mix. More than 80,000 apps target children. Germany's Fox & Sheep, a children's app developer and publisher in Berlin, started with two apps in 2012 and has now launched 29, all aimed at children ages 2 to 6.

For busy parents comfortable with technology who want their kids to benefit at an early age, apps offer creative ways to play, even taking traditional activities - say, reading a book or playing dress-up - into the digital world. Often, these apps fit millennial values, which prize creativity or global experiences.

For most everyone else, there's still confusion about what technology is acceptable to introduce to kids, especially little ones.

Warren Buckleitner, editor of Children's Technology Review in Flemington, N.J., helps parents avoid commercial content and maximize the benefits with Buckleitner's Guide to Using Tablets with Young Children, released Aug. 1.

Even children as young as 2 can enjoy "turn-taking" apps with their parents that often use the tablet's camera. Toca Hair Salon Me lets families create funny, wild hairstyles on themselves and even their pets, and MSQRD allows users to trade faces - to comical and often creepy results.

Beyond the enjoyment and bonding experiences, these apps can stimulate language, "like electrodes to conversation," said Buckleitner.

"A very good app for small children doesn't show advertising, has little tutorial and explanation texts, and works intuitively for children," said Verena Pausder, founder and CEO of Fox & Sheep.

"Even infants are bewitched by phones and tablets," said Joel Nichols, the data, strategy, and evaluation administrator for the Free Library of Philadelphia. "They love a glowing screen, and storytelling is a good use for the device."

He warns that parents must be actively engaged for there to be any educational benefit. "Otherwise, it functions like TV that doesn't necessarily have any educational outcome."

Although apps like StoryKeepers, Scholastic Storia, and Incredebooks enhance storytelling, they will never replace books, insisted Nichols. "Paper books don't need any power, you can't drop them and break them, and if you drop them in the bathtub you have to dry the pages but they're not going to get ruined," he said.

Nichols and his son Jamie, 3, enjoy 3 Schweinchen, the German Three Little Pigs, by Carlsen Verlag GmbH. The app lets them interact with the characters, giving the German language context. Jamie can touch things on the page to make the characters react.

"It's been exciting to see him tell the story in a very 3-year-old way that has plot and action and order," said Nichols. And, he's learning German at the same time.

Though some worry their kids are getting too much screen time, others worry that if they don't expose their children to technology at a young age, the youngsters might fall behind, Nichols said. "They see it as a whole literacy and educational package."

Jennifer Walker's son Oscar, 3½, loves the Squiggles drawing app, which animates his scribbles. "There's a variety of different backgrounds, colors, and patterns," Walker of South Philly said. She's amazed at his attention span - up to 20 minutes at a time. "The animation element livens it up so it's different than just drawing on a piece of paper, but it mirrors regular drawing on paper so you get some hand-eye coordination."

One highlight of app play, said Buckleitner, is that kids have the ability to control screen content - as opposed to watching it passively. "A child learns by being active and being in control," he said.

Petting Zoo and CHOMP are two popular apps developed by illustrator and author Christoph Niemann, who believes apps should surprise users.

Petting Zoo, downloaded more than 2 million times since its 2012 launch, uses "old-school classic" black line drawings that you touch to come to life. "It was a retro idea that required a lot of state-of-the-art technology," said Niemann. "In technology, certain things are possible in terms of visual complexity that were not possible five or 10 years ago."

CHOMP is like dress-up. It uses the device's camera to show the user's face, creating a character in a drawn universe. The user can touch props to create a story.

"To just see your face and the rest of your body is drawn, you are almost in a costume," said Niemann. Children will enjoy being a bug or a cyclops, and their parents will appreciate the literary references of the books' authors, Kafka and Homer.

Introduced in January, CHOMP already has been downloaded more than 1 million times.

Still, using technology shouldn't replace other forms of play, said Buckleitner.

"That can be a detriment to child development," he said. "You need balance - a trip to the zoo as well as apps that let children learn more about the animals. Every parent has a feeling in their gut of when it's time to turn it off and go outside."