Looking at a new to us car

So preface this by saying my kids are:
G-9 years old will be 10 in March
C-7 years old will be 8 in January
M-5 years old newly

So we are looking at a new vehicle and I was hoping to be able to use the seats we have. So we are looking at a smaller car like a civic, or a elantra, or something like that.

I will keep the big seats in my van. That leaves a Radian FF for M, and a literider for each G and C.

What do you think are the chances we can fit this combo in most small cars? This will be a back up vehicle and none of the kids will be in it a lot mostly in town rides of less than 15 min.

Am I Crazy or do I need to look at Highbacks for the older two?

DH just got an Elantra after his Accord was totaled. My kids are almost the same ages your three (just turned 9, 7.5 and 5.5). We looked at the Civic, Corolla, Focus, and Elantra - he also drove a Sentra and maybe one other in that class.

I fit a Maestro in the center with Literiders outboard in the Focus and Elantra (the only two that made it far enough to test seats out). The Focus had boatloads of room, the Elantra was tighter but works if I buckle the boosters. A BubbleBum makes it much easier. I also did not try the Maestro outboard with boosters center/outboard, which might be easier as well. I didn't bother with my Radian since I could make the Maestro work. Mostly, we only have one or two kids in that car at at time, so three across is not a daily need.

I will say that the center seat in the Elantra has a much higher back/headrest than the Focus. DS1 (9yo ) could not actually use a backless in the center of the Focus (ears over the headrest) where he could in the Elantra with a few inches to grow. I think he will be able to use the center position until he 5-steps there.

I am actually OK with them going backless in that car. The safety features are a pretty big upgrade from the previous one and were way better than my previous van (02 Ody). They are not in there that often and not for long trips where they may be tempted to slump over.