They look feathered out pretty well. As long as there's a draft free spot for them, it should be fine with those temps. If it's below freezing when I move chicks outside, I just set up the heat plate so they can warm up a bit, if needed. If your coop doesn't have electric, you can always run an extension cord to plug in the heat plate. If you're using a heat lamp, just be careful. If it gets knocked over, it can start a fire quickly. You can always put a box, sideways, on the coop floor for them to snuggle up into on cold nights.
They look good so if they're fully weaned off heat, I would take them out for some supervised visits outdoors for a couple of days and see how they do (and to further acclimate them to cooler temperatures) and if they handle it well, they'll be good to move out.
If they have access to grit they can have a bit of extras, but their feed should continue to be the majority of their diet.