We have a small car (VW Polo). I'd like a bike rack that could fit my children's bikes. Children are age 4 and 7. I was reading the reviews for some racks and it said the small bikes didn't fit on. Bonus points for one where we can still open the boot with the rack attached, although happy to take the bikes off to open the boot. This isn't essential but would prefer to fit the rack the day before to prevent stress in the morning!