Did the authors propose any solutions?

I don't think anyone with a shred of decency wants children - citizens or otherwise - locked in detention cells. On the other hand, if the parents are inadmissible or considered a flight risk, the law must be applied.

There is a women's minimum security detention facility near to my workplace. It's a bunch of self contained houses with yards, shared facilities, even gardens. It's perfectly humane, but it's fenced and guarded. Maybe we need to consider holding these cases in places like this. The children could be allowed to come and go (with appropriate non-detained adult supervision), but the detained adults wouldn't - at least not until their case is resolved one way or another.