The exposure is as serious as it gets
An injury to a child in your care produces a claim with few practical limits on its size. It is also the kind of claim most likely to be pursued fully, because the claimant is a family protecting a child. This is not an area where a gap is survivable.
Personal policies exclude it by name
Childcare for payment is a business pursuit. Homeowners liability, renters liability and personal umbrellas all exclude business pursuits, so the activity with the largest potential claim is specifically outside the cover a household already holds.
The right answer is a childcare liability policy
Cover written for home childcare exists, it is not expensive relative to the exposure, and it is available whether the arrangement is licensed or an informal few children. Watching friends’ children for payment counts.