The best suggestion I have for ergonomics of cleaning and washing a minivan frequented by multiple children is to marry someone who likes to clean your car for you. Wouldn’t that be nice? If that isn’t going to happen, then clean it in the coolness of the morning or evening. Best of all, get your kids to help because they can easily get the low spots and maybe if they help with the cleaning they will think about making a mess on the inside, possibly. LOL Most importantly, have fun with it. Follow Mary Poppin’s suggestion to make cleaning fun. Get wet, quirt each other with the hose, sing, and play. That makes any job so much easier.