ShinyAndNew - HOW HOW HOW please write a book and have it published ASAP
Is it acceptable - it depends on a variety of factors. Are the children happy? Do they play the DS and watch TV all day or it it something they do in the morning and then go out and do things with your wife for the rest of the day?
Getting up at 8 or 9 is not necessarily a problem if you have nowhere else to be. She might be a much "nicer" mother for having had that extra hour of kip.
Something you should broach with her? Unless there are problems arising from this situation, I dont think you should presume to lecture your wife on how she is choosing to raise your children, within reason, when you are not there, unless there is a specific issue that bothers you - a definitive safety issue, for instance. Not just because it sounds kind of slack in the face of it.
We start our day in a very relaxed manner on a non-school day - it usually involves watching TV in my bed, sometimes not going downstairs until after 9. At the moment, I am dressed, but neither children are, yet, though I will be dressing them shortly - there is nobody here to see us or judge us and we are having a lovely relaxed morning. They are currently playing with a jigsaw puzzle and I am mumsnetting. Slack? You betcha, but everyone is relaxed and happy.