Part of the reason I feel so strongly about this issue, is that I was accosted and abused by a man in relation to a similar situation when I was 38 weeks pregnant.
The circumstances were that I was heavily pregnant, with pelvic arthropothy, and a 2 yr old who wriggled, kicked and fought every time she was put in the carseat. I physically couldn't handle her, and had a responsibility to my own health and unborn baby. I needed to get milk, so I popped into a corner shop to get some. I was parked in the layby immediately outside the shop, and had the (locked) car in my sight the entire time I was in the shop (max 2 minutes). I had told my DD where I was going and she was completely happy. I knew she was happy, because I could see her, and she could see me - we were pulling funny faces at each other through the window.
When I went back to the car, a huge man came running towards me screaming at me - I seriously thought he was going to assault me. He was shouting how dare you leave a child in a car unattended, and stood between me and the driver's door so I couldn't get into the car. He continued to tower over me and scream in my face.
I felt completely vulnerable and intimidated by this man (remember, I was 38 weeks pregnant). I told him to fuck off, and that it was none of his business, and if he didn't get out of the way I was phoning the police, which I did. (I came across a lot braver than I actually felt at the time). The man told me he was phoning social services and that he had taken photos of my daughter as evidence.
The police were completely supportive of me, and reassured me I had done nothing wrong. They contacted social services on my behalf to see if the man had contacted them (which he had). I spoke with a child protection officer, who again completely reassured me that I had done nothing wrong. Both the police and social services encouraged me to pursue a prosecution against the man for assault. I didn't because I just didn't want any stress, being so close to having a new baby, and I was fearful of having anything more to do with him as I thought that he must be a bit unhinged.
Even as I type this, I am so angry that a random stranger felt he had the right to bully a clearly vulnerable woman, and use 'child welfare' as the weapon. If he was so concerned about child welfare, the man would not have screamed and physically intimidated me in front of my child.
I know this is a really extreme example, but it illustrates how we have become so fearful about raising our children - and in my case, I think the fear is over interfering strangers and the threat of social services, rather than the albeit possible, but mostly unlikely risks of flaming cars, paedos, drunk driving, car stealing thugs, and window smashing police officers.
It is from this background and perspective that I say YANBU.