Free range is a risk no matter where you are. Even in an urban backyard, with a regular neighborhood fence, free range birds can become prey. However, I’d doubt you would have a raccoon problem during the day-have them in by dusk, don’t let them out before it’s fully light.
Foxes are...
Yes, you may have an issue. The raccoons can climb into the enclosure-the tarp will not keep them out -even when secured. But, if your builds are closed tight with an actual latch a toddler could not open, then that might be ok.
Foxes can dig and climb, but I’ll assume they would dig first...