Don't.
Simply put, it's a mistake. If you use technology purely to increase your students' engagement with their learning, then you are wasting your time, and more importantly, your learners' time.
Yes, it may happen that you can perceive an increase in students engagement when using technology, but that is not a reason to use it. This is because as the technology becomes embedded, it loses its initial excitement, the novelty factor, and becomes another facilitator of learning. Like a pencil. An incredibly powerful and effective pencil. But still like a tool to be used for learning. How many teachers claim to introduce the use of a pencil to increase student engagement? None, you'd be mad to. Unless pencils are used so infrequently that they then become a novelty, then they may work, briefly.
Guess what? Technology such as iPads are not a novelty to students. So many have them, or have used them already that although they may be new to the teacher, they are not actually that special to the students. Being allowed to use them in school is a novelty. But that soon wears off if you are using them to achieve the same things that you have always achieved. If one of your main foci is to increase engagement, then there is the temptation to miss the opportunity to take learning to different levels. In fact, if engagement is a substantial issue for your class, then you probably need to take a hard look at how you are organising learning in your class anyway, never mind throwing technology into the mix.
The novelty of technology increases engagement for almost all students. But as soon as the tasks on technology becomes schoolwork, then play becomes work. If the students are not motivated by their schoolwork, it doesn't matter how it is completed, they'll still not be motivated.
