To tell friend not to drive 4 yr old without car seat?

A 4 year old should be rear facing so this sounds absolutely nuts to me. It just takes one accident and your child would go through that windscreen.

Can they not get public transport or an alternative way to get there for a day out?

The taxi rule is only really acceptable in emergencies and even then the child should be sat on your knee, they won't let you put them on a seat at that age!

I would just send a booster for the 4yo, but it depends on the road type and I know some people fret about them. If you don't want a booster then you'll have to find alternative childcare unfortunately, you can't request childcare and then alter their plans.

Yabu to expect them to take two cars

can you drive your dc yourself?

I’m sorry but this is laughable. Smoking/Vaping/Alcohol/Jumping from an 5 story building, also all legal, not safe though are they. What a stupid comment.

If it was me I wouldn’t let my child go, even in a booster seat but I’m a rear face until 7/8yo parent. I’d suggest adult in back between 2 seats and another car seat properly fitted, air bags turned off in the front.

Personally I wouldn’t take the risk, and I’m surprised another parent is willing to allow it. I wouldn’t dream of it. How it is legal is beyond me.

Just to clarify, some people have stated the " if it's legal it's safe," and that is certainly not the case. It's legal for example to put 2 yo forward facing... Doesn't make it safe!
Neck injuries are still going strong at his age so I understand OP.
We've got a booster at home for when we've got no other alternative (taxi to the airport, or taxying when abroad).
When we visit my parents in Spain, we've got no other option as to use a high back booster over there (which I'm not thrilled about).
But when in the UK, our 5 yo (who has a huge head!) will continue to go onto his ERF until car seat height allows, which I think is 125cm.

I'm not sure why people think that car seat safety is something to joke about :( ERFs actually make the difference between an alive or a dead child.

when I had my third child we were told about this law by mamas and papas when I went to get a car seat fitted. My oldest was 6 so. Or as young as yours. They said not to be tempted by the car seat in the the front, that it’s actually safer in the middle seat of the back row without a car seat than being in the front seat with a car seat. I have frequently travelled with a younger child in the middle of two car seats and it worked out ok. I get that it’s concerning and seems alien, but personally I wouldn’t ask my friend to take two cars.

The belt won’t hold a 4yo. Your child will not be protected properly in case of an accident. It’s not safe.

Just cancel and look for other childcare.

If you put oldest child in the front with a car seat (airbags off obvs before I get a Mumsnet lecture) then an adult could sit in the back and all children are in a car seat. I’ve done this before when I had 3 that needed a car seat - although I was on my own so didn’t have to squeeze an adult in the back.

I just checked out the data and NCMD records 16 deaths of children under 5 over 3 years from UK as passengers in cars. This is less than 2 in a million kids. I couldn't see any info of whether these children had even been in child seats.

Basically very rare, I wouldn't lose sleep if taking reasonable steps.

Have you seen the bubble bum car seats? I find they fit between 2 car seats but obviously depends on size of the car. Link here in case it helps:
amzn.eu/d/h395qqc

I bet you can … once she’s in she can just shove the seats over a bit, it’s only half an hour.

☝🏻 this … we used to do this.

In this situation if I had three kids to transport I'd put the oldest in the front seat in a car seat, and have the smallest adult sit in the middle at the back. I've sat in this position several times. Not that comfortable but fine.

She will be fine if it's legal it's safe if you aren't comfortable find alternative childcare

Can't your child sit in front seat with their car seat and the other parent sit in the back with the two car seats?

I would ask them not to take them, I know they are doing you a favour, but god forbid something happens

I think if you ask them to take two cars, you might find you don't have childcare.

For a 4yo a seatbelt will still restrain them, particularly from ejection and head injuries which are the two biggest dangers in a car accident. They will also gain some side impact protection from being physically further away from the sides of the car and being behind the other two car seats. They are less likely to hit their head on the seat in front because there is no seat directly in front of them. The vast vast majority of cars on the road today have a full lap and shoulder belt in the centre (not just a lap belt).

The reason 4yos are normally legally required to be at least on a booster cushion (preferably in a full high back booster or even ERF seat or 5 point harness) is because their legs are normally so small/thin and their pelvis isn't large enough for the lap belt to be seated properly, over the pelvis. (Top of thighs touching the pelvis is also OK). Seatbelts are designed to rest over the pelvis because it's a strong, solid body part and it keeps you pinned in place in your seat. In younger children, the "arms" of the booster seat keep the lap belt in the right place.

So if they are in an accident and not on a booster seat, the danger is that their pelvis slides under the seatbelt, and the belt tightens onto their abdomen which is much softer and contains vital organs so you don't really want it taking a load of force in an accident.

It's not great. It's not as big of a danger as head injuries or going flying out of the seat - which is why it's allowed as an exception. But you get better outcomes on average when primary-aged children are at least in a booster seat positioning the lap belt properly.

Seatbelt is definitely better than nothing at 4.

Backless booster better than just the seatbelt.

High back booster (or other type of child restraint if child fits) best of all.

Don't be tempted to suggest she sits on a cushion or a thick book or similar BTW - it has to be a booster seat because only a proper booster seat has the arms or clips which secure it to the seatbelt. A cushion is not secured to anything, so is potentially worse than just the seatbelt on its own. And avoid the dodgy polystyrene booster seats on amazon which just have fabric flaps as the belt guides. I don't actually think they meet guidelines despite what the listings say. Bubble Bum isn't the best thing for a 4yo, but it is properly tested, should fit between two seats, and ought to be an improvement over the seatbelt if you decide to let her go.

I would not let my children go in a car without a car seat and they are much older.
I would look for different childcare arrangements as to expect them to take two cars seems unreasonable and an extra cost.

I’d want the 4 year old to have a booster seat, even if just a simple narrow booster .
Otherwise they could
stay at home
take 2 cars
you could find alternative childcare.