Let sleeping puppy sleep

I took little Prints around to the office, he emptied the bin and played with a few empty boxes then promptly fell a sleep on my lap. This is all very sweet, but he is going to grow up into a very big dog and won't be able to fit on to anyones lap then :-( ……………………..do I tell him now of wait until he is a bigger boy so as not to ruin his puppy hood LOL