My OH has a Chevrolet Equinox, and a booster, a front facing and a rear facing will fit but BARELY. I'm assuming this is your car seat configuration right now. I would ONLY allow OH to take the kids in that car in the case of an emergency. When we had 3 kids, we got a Honda Odyssey, which fit 3 across. My kids were 2 1/2, 11 months and a newborn when my third was born, and they were all rear facing in it, and it fit just fine. We actually split 2 car seats up so they were on either side of the car and put my oldest in the third row and accessed his seat from the trunk. It was just easier to reach.
When my fourth was born, it was a pain because we had no trunk space anymore since my mom now lives with us and rides in the car with us. I now have a Mercedes Benz Sprinter. It's a big 12-seater van with a huge trunk (and headrests, which those "Church vans" don't have, and I'm not willing to risk my kids' necks later on. I plan on keeping this one forever, and I LOVE it.
So here's my advice. If your oldest can buckle himself into their seats safely, and you might have more kids, I'd look into the Honda Odyssey. It was a great car. I have had my current van for a little while now, and although it's nice and comfy and very spacious, I still really miss my Odyssey. I recommend the Odyssey to everyone who comes to me saying, "I'm having my third! They won't fit in my car! What do I do?" I get asked that a lot. hahaha. If I didn't think I was gonna have 5 kids, I would have kept the Odyssey.
I'm still mourning it.