Our two year olds like Babygames, Doodoo Lite, Farmyard, Toca Train, Peppa Paintbox, Old McDonald, Talking Ben, Ginger and Memory Match..
The five year olds like Minecraft, Smelly Cat, Hay Day, TicTacToe, Bridge Construction and Lego Starwars.
My favourites, apart from banking and shopping apps, are Night Sky, Longbow Lite, Tetris, Hay Day (I maintain it for the kids!), Bubble Blaze, Sudoku and Chirp (birdsong identifier).
The EasyJet app is great for flight bookings, easy access tickets and boarding cards and lots more.