Yes COAsT (the online section) will work on an iPad, computer, Kindle Fire etc.
There are CEM-style and GL-style tests available. Most of the GL Tests are archived, so tick the archived box to see those ones.
GL-style VR = past mock papers 2008 A-C, 2009 A-E, 2010 A-E, 2014 A-C and Practice Papers 1-8
GL-style maths = past mock papers 2009 A-E, 2010 A-E, 2014 A-C and maths practice papers 1-5
GL-style English = past mock papers 2009 A & B, 2014 A-C
GL-style NVR = past mock papers 2009 A-E, 2010 A-E, 2014 A-C
CEM-style (mixed subjects) = Numerical & NVR past mock tests 2015 A & B, 2016 A & B, 2016 A & B, 2017 A & B and 2018 A & B.
= English & VR same as above.
There are also CEM-style practice tests A-E (2 papers for each test- mixed subjects in each paper)
Some of these tests can be printed and others have to be completed online (they are then timed in sections).As a parent or tutor you will be able to browse any tests/exercises before you assign them to do to ensure that they are suitable for your use.
If you need some more advice please do ask.