2nd step car seat help

Ok, so right now my little one is in the Graco Snug Ride 30. When I have my son in March, we’ll then use that one for him. It’s been really nice that it attaches in a base because my mom and I have to take turns taking my daughter to and from day care due to my work schedule. We’ll have to do the same when my boy gets here, so what’s a good recommended seat for her?

Side note: I’ve looked at the 4-in-1’s and the forever seats, or whatever they’re called, but the con is that they stay in the car and I don’t want to spend $300 on that seat for my car and have to spend another $300 for my mom’s car.

Help!