Grandma transporting different kid combos

[Growuphelen]

I provide childcare for my grandkids in different combos 3 days a week and need to choose a new car seat for the almost 4 year old. My question is does a 123 seat convert easily from the 4 yr old/20kg option that I need on a Tuesday ! To the 15mth/10kg option I need on a Friday ! I can't have two seats because I already have a 123 in for the 18mth old who I transport both days.

I don't know the answer to this, but you'll probably get more replies if you re-post in Chat with 'car seat question' or something like that in the title. There is more traffic there so it will get a bigger audience.

Thank you

I think the shoulder straps might be a problem. You'll want them lower for the baby than the 4 year old. We have a brittax first class and it covers the age range you want (my 4 year old was still in it when his baby sister came along) but it does need customising (just the shoulder belts really). Changing them is a faff and means taking the car seat out of the car.
Is the 4 year old big enough for a high backed booster? These use the normal car seat as a belt.
But I appreciate you don't want two car seats.
K

We have a 123 for our two year old. If you look for one where the shoulder straps and head rest adjust together (so when you move the headrest the belt position moves too) this is easier and you don't have to take seat out. Also it has more possible positions.
We did have a britax first class plus which is a group 0/1 but I found it quite small for ds so move to a cosy'n'safe 123 that has a recline function (as a lot of 123 don't) which is great for a smaller sleeping baby and the harness is suitable for up to 25kg as opposed to 18kg with most so can have harnesses for longer before changing to seat belts (which I feel is safer) I'll look for a link to the seat I have.

www.toysrus.co.uk/mobile/toys/cozy-n-safe-group-1-2-3-excalibur-car-seat/TRUP2255790001

I have a Kiddy Guardian seat which I use when taking my nieces/friends kids out. It works as a high back booster for 4-12's and uses an impact cushion, so it's suitable from 9kg too. No straps to adjust or remove, it straps in with a seatbelt and its light enough to transfer between cars easily if needed.

I also have a Kiddy Guardian Pro for both my children - ages 5 and 23 months.
It's suitable from 15 months with the impact cushion as Nanny mentions. The only problem I have had with them is, my son (when about 16/17 months) managed to wriggle out of it mid-drive. We ended up buying a mothercare seat with straps (which he still got out of, just less easily), but he is fine in the Kiddy Guardian again at nearly 2. We never had that problem with our daughter at all, but my son is a Houdini who gets out of any sort of restraining device, so it probably depends on the child.