This won't be the answer you want to hear but it's very difficult to say because we don't know what child seats you have. It's quite difficult to find a car that's wide enough to take three seats in one row, though, so I'd start by checking out this Top 10 that I wrote for our parent site, heycar: heycar.co.uk/blog/top-10-cars-take-three-child-sea...s

As it says in the copy, not all of these cars have three Isofix points, but they should be able to carry three child seats along the second-row. If you have larger child seats, test the car before you buy. Dealers will usually let you try the car out by putting your child seats in to see if they fit. Obviously, that'll have to wait until after lockdown, but it'll be worse to buy a car and find that the seats don't fit.