I would say generally it's ok if you know the routine suits and he is basically well slept. If you feel unsure maybe allow an extra 15 mins nap on somewhere, perhaps try it at the weekend when there is no school run to see how things pan out? 2 days may not be long enough to tell but then again it might, you could see if he is either in a better mood or if BT ends up tricky to get him down.