Thank you all for your suggestions and reassurance. I have great angst about a newborn crying it out and would do anything to avoid that happening at daycare.
The great news is that I have been persistent about having him be comfortable on the floor. He's not a "carpet gnome" in that I can't yet leave him alone, but he is playing up to 20 minutes with me sitting right there with him. If he gets very upset I hold him for a minute to give him a break or change position (black to tummy or vice versa) and put him right back down. I will gradually leave him alone longer and longer.
I read some stuff on RIE and it gave me confidence to let him work stuff out on the floor.
My first was held all the time (he didn't tolerate ANYTHING else-swings, bouncers, carseats, let alone floors) and he still, at 6, has a really hard time entertaining himself
