Can anyone who has used the Minni Vans tell me if their car seats convert to a booster easily and will cast members do it. We have an 8 year old who will need the booster and a 3 year old who will need a forward facing harnessed seat. Just wondering if we have to buy a separate booster to take with us or whether she can use the Minnie Vans car seat in booster mode. Thanks so much!