Number of infants not on booking form

Our cottage sleeps 4 + 1 baby. As far as a guest is concerned a baby is a child and should therefore be included in the number of children, but the system makes no distinction between children and babies in the capacity of the property. If I say the the property sleeps 4 + 1 child, it certainly won't fit a 10 year old child who requires a bed. If I say the property sleeps 4, then the system says that the number of guests exceeds the capacity of the property.
Is there a way around this?

The way I treat this is that I have max occupancy of people of ANY age. if my max occupancy is 10, I do not care how old are they - they can be 1 day old or 100 years old but total should not exceed 10. I think your situation is one-off. Maybe do not include a baby at all in settings but explain in verbiage.

It is essential that this information gets collected at time of booking in order to have cots and high chairs ready and most importantly, protection around swimming pools.
This is irrespective of the occupancy policies but it should be in line with the major portals settings which is that infants are non-paying guests and are not accounted in occupancy totals.