LEGO Harry Potter: Years 1-4 and LEGO HP: Years 5-7 are down to 79p on the iOS store! LEGO Jurassic World is also this price (http://www.hotukdeals.com/deals/lego-jurassic-world-ios-apple-79p-itunes-2579352)
Could be a nice addition as a Christmas present :p
There's a lot to do in these games and they're usually around £5 so they're well worth 79p! If you've got an iPhone and are wondering how well they'll play on a small screen, try downloading LEGO Star Wars: The Complete Saga which allows you to play the first level or so for free. This will give you a good feel on gameplay. I find the Classic controls are a lot easier to use than the Touch controls.
I preferred 1-4 as you had to draw the spells so it gave it a nice interaction with the game but they're both really fun. I've not played Jurassic World so I'll be downloading that now!
Link for Years 1-4: https://itunes.apple.com/gb/app/lego-harry-potter-years-1-4/id404086528?mt=8
Link for Years 5-7: https://itunes.apple.com/gb/app/lego-harry-potter-years-5-7/id501220013?mt=8
Link for Jurassic World: https://itunes.apple.com/gb/app/lego-jurassic-world/id1073698593?mt=8