
Hi there and welcome to BackYard Chickens!!
What is sand on plywood? Is that a tray under the roosts filled with sand to easily scoop out poo? That's a wonderful idea. But I don't think I would recommend a wire floor... chickens love to scratch, and wire can pull their claws or cause bumblefoot, not to mention it's just uncomfortable to walk on and poo will get caked and be impossible to keep clean. Although wire buried under the dirt would be fine to keep out burrowing/digging predators. Half inch hardware cloth would be even better fencing for the run and/or to cover any windows/vents to keep out snakes and mice.
Have you looked at the
Chicken Coops section for ideas?
Also, you can start playing with those cute babies any time now! They usually only need a day to settle in and learn what food & water is. As sourland said, reaching for them from above can be scary, so move your hand to ground level first then try to reach
under to pick them up, then cup your other hand over their back to keep them from falling. Mine used to hop right on my palm to get lifted out of the brooder.
Here are some of my favorite helpful links that may be of interest to you:
Kick The Heat Lamp: Better, Safer And Healthier Options To Heat Your Brooder
Chicken Coop Ventilation- Go Out There And Cut More Holes in Your Coop!
How to Raise Chickens -this one has tons of links to other information
View attachment 1531014 Well I wish you the best in your new chicken adventure!!!