Hi there we have recently become new foster parents to 2 girls. 1-2yrs 36lb and the other 7 42lbs. What is the best seat to get for them.I drive a 08 caravan, i would be putting them in middle seats in back. It has been along time since I have had to think about this as the kids I usually deal with have seats of their own privided by the ministry. Help please and ty