I have a P5 LE and love it. We have 12 grandkids and they also love to ride in it.
There is a few things I would suggest before putting kids in the rear seats and in the front middle. There is a heat problem under the seats, we all know it. So some added heat shielding, a pool noodle between the bed and front seat back, and a fan or fans to help remove some of the heat is a must if you plan on using much in the hot times of the year.
I have not installed any car seats in mine, but pretty sure you can make them work and keep the kids safe. Make sure you use the rear nets. They do a great job to stop the limbs from slapping passengers and keep hands inside.