This approach has several advantages:
- it is simple and would work
- child restraints in rear facing adult seats don’t carry high crash loads. The cushioned seat back will do the job, and distribute the load in an optimum manner. A baby belly belt might even be enough for positioning the child and for turbulence.
- those parents and children would (typically) be near a lavatory, floor level emergency exits, and possibly a galley, for their convenience
- with many airlines, they would board first, and have more time to get settled