Got our switch on a spur of the moment purchase yesterday.
Loving it today, the 3 year old manages to play mario kart and some of the mini games on mario party. We then went on to play oddysey. Thought it would be fine if our 6 year old daughter was mario and 3 year old son was cappy. Unfortunately our son found the jump button and caused our daughter to die continuously, didn't go down well. I'd advise only kids 5+ play oddysey, even as the hat.
Obviously when the kids are in bed we play a bit, can't wait to complete oddysey with the Mrs.
My six year old completed Odessy on assist mode (I helped with some of the tougher platforming/timed bits). Was a great experience to share