funny thing is, i got both my kids R4's... they are two and seven... and the same game rivalry is a thing with them too... I went with R4's for the cheap and established factor... and, yes, they are good and do what they should, and are well built as well...
the only problem i encounter is they can delete games and or saves... not a problem with my seven yr old, but my two yr old has deleted both games and saves heh... now this really doesnt pose a problem as she just loves to play, so reload the game and she is good to go... the saves, meh, easy enuff to redo as well, so not that big of a problem either... long as your kids get along and wont delete each others saves in a fit of anger... all is good...
as an alternative as i have been trying alot of the better cards out just to see what all is good/better... I would have got my kids the Edge card, and am still thinking to switch over to it over the R4 for them... it is every bit as solid as the R4's, holds more skins which they love, yes 12 is plenty, but 30 is awespme... why switch? the edge has impressed me greatly in it is the same interface style with 3 buttons, but faster and overall nicer... it also changes how the games are listed over the R4, to me a vast improvement as it only shows the name of the game... no numbers or other nonsense... plays movies/music/runs all homebrew now at least the same if not better... both are the same price roughly if the edge isnt cheaper even at 50-55 bucks...