Please DO NOT (and yes I am being very emphatic here!) use eucalyptus oil or any essential oil for that matter on anything that will go into a baby's mouth or be in close contact with their skin.

Eucalyptus especially is highly toxic as well as a skin irritant.

Personally I would just stick to vinegar - most cleaning and disinfectant products are dangerous if ingested. Dishwashing detergent is OK because it's designed to be safe for use with food handling equipment.