What does your local building authority allow? What's common practice in your area? That's the place to start.

I think that your husband is being unreasonable in his fear regarding plastic and concrete. It's used often - PEX in particular is often used in slabs including for radiant heat.

Concrete always cracks / shifts / settles not to mention freezing. I'd much rather have a flexible pipe in/under the slab than something that will break when the concrete shifts.

Even so, I'd look at how to avoid the slab entirely (go around) if you can.

Note: they have been using PEX in Europe much longer than here. It's proven stuff.

If code allows why not run the water line through a sleeve. That way no contact with the concrete. We have used inch and a half pvc on a couple of slabs to run the water line through. Or, as mentioned go around the slab.Just a thought.