Any autumn colour clothes, beige, white, green, mustard, orange or similar. All the shops are full of those colours at the moment. So that should be no problem at all.
Christmas Pjs would be the easiest. But you can go for any Christmas clothes. The best place to buy Christmas Clothes right now is Amazon, please check the delivery date before ordering. I also have a choice of Christmas Clothes and Pjs. So let me know if you are stuck and the size of your kids.