Jeff,
I've got an 8yr old son and a 13mth old girl and another one on the way. Early and late is the only way to go. I often also use the stages method. I also have my detailing business at least 2 weekends a month.
Remember you should only be having to put in some heavy time, 6/10hr, on the vehicle every 4/6 months. the rest of the time 60-90 min/wk should be enough for upkeep
The only other option you have is to get a trusted detailer that you know or have references from. Pay the $150 to get the car in mint condition and then just do the upkeep i.e. weekly washings, QDing, dressing tires etc. I'm not talking about some hack you have to make sure the guy is going be worth every penny. If you find the right mobile detailer they may be able to free up somemore family time.