PET containers for freezer meals? I'm looking to develop freezer meals for my family. The meals will be frozen in plastic takeout boxes likely PET, or PET-lined paper/kraft bowls.

The frozen meals are likely to remain frozen even when opened by lunch time, and will have to be blasted in a microwave at medium for 15 minutes, or at high for 5 minutes. Either of these are practical and potentially unsafe.

It's the unsafe part I'm worried -- do these plastic boxes or paper bowls that say "microwave safe" really suitable for high power microwave?
Not all PET plastic are microwave safe; make certain the containers you buy are labelled as such.

see this link.

"Unlabeled plastic containers aren't necessarily unsafe for the microwave. But the lack of label just means that these plastics haven't gone through the battery of tests required to ensure microwave safety. Because there's no way to tell if these containers can hold up to microwave heat, it's best not to use them in the microwave."

and this; 

"Many of our manufactures do not recommend HDPE for the microwave and we suggest that you avoid it unless the manufacture has specifically approved it. PET and polycarbonate should not be used for microwaving as they tend to absorb heat."