Help booster seat advice needed

[2greatboysandabump]

We have a vauxhall meriva (55 plate) and have a Graco Junior Highback for our DS2(6) and have bought a maxi-cosi pebble with family fix base for DC3 due in June. The problem is the seat for DS1 who will be 9 when baby due. He is quite small and is currently using a Graco Junior booster seat (with highback removed) which definately doesn't fit.

I can't seam to find a booster seats which is slim enough to fit between the buckles. Can anyone help? I'm also concerned, since reading on mumsnet, that he should continue to be in a highback booster. I am prepared to buy any booster/highback booster, if anyone can suggest one which fits.

We bought this car 12 months ago expecting it to fit 3 children in the back, especially as the boys will be 6 and 9 when baby arrives. Saw an episode of Supernanny with 3 children in carseats in the back of a meriva so will be gutted if there isn't a combination which fits.

the britax adventure is narrow you may have to get two so they will fit. The graco one does seam to be wide the other ones that may fit are the maxi cosy booster with back and the concorde carseat. You problem is because you have one on isofix you can push that one nearer the door which is how people often get three across the back. If you put the boosters with backs next to each other so the do up un the same place with the biggest child in the middle as you may need to slide the other one out a bit to strap in and then slide back. may not be easy. When baby is in stage 2 car seat you could use one of these in the middle seat www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_38 5057langId-1categoryId165597
We use one in between two seat in a clio. What about putting the baby in the front when it is only you and the children.