Car-buying petrol (on Lpg) combination SUV

Hello together, I am about to make a decision. I wanted to buy a used car. I drive about 10 tsd short distance in the year and 3 to 4 times long (1.2 thousand) in total per year I make between 16 to 20 thousand kilometers. I/we need a combi or a larger SUV, plenty of place for prams, MaxiCosi and children’s clothes I thought of buying a used car for max. 18 thousand and converted to LPG. I couldn’t decide between a BMW e61 (best 550 i) or a Volvo V70 or XC 70 or XC90. All are robust, gas-resistant and safe. At the BMW I’m a bit afraid because of serwice, but I’m a screwdriver myself and can already do several things myself. What do you want me to do? P.S. I don’t want anything from VAG, Opel, Fiat Ford