I need to get a seat for my MIL's car. It won't be used often but needs to fit my 6.5 yo. and 3.5 yo. who both weigh 40 lbs. It needs to be a no rethread adjust so she can do it easily without uninstalling the seat. Budget is also under $200 and even better if it's closer to $150. With all that I'm looking at the Britax Pioneer, Graco Argos, and Harmony Defender.......I looked at the Pioneer today and it seemed ok, going tomorrow to see the Argos and Defender but my biggest concern is which would be the easiest to install. She has a Lexus SUV (smaller sized one) if that makes a difference. Can anyone help me out? I am so torn between them and at this point just need to pick one and be done.