Sadly we are past the end of the cyclocross season. If you had posted this a few months ago, I would have shown you a Renault Zoe packed up with the following:
45 litres of water in 2 containers
Rollers
Bike stand
Track Pump
Tools rucksack
Trolley for carrying most of this list (festival trolley)
Collapsable chair
Umbrella, 3 coats (thick, thin and waterproof), walking boots, large towel, small microfibre towel, various cloths
Possible change of clothes
Lunch, including a camping stove and pans
Jet wash (and two batteries)
2 bikes
1 loose wheel, because I can't fit 2 bikes in the back with wheels still on
1 wheel bag with 2 wheels
Cycling shoes
Helmet and other cycling items (sunglasses, glass cleaner, buff, overshoes)
Number plate board and bungee cords. (bike rack goes on the outside, whether it is used or not)
Additionally, if the event is over 50 miles, I will need to consider charging options, so the weekend schedule will identify where and when I can charge, either overnight or during a meal stop on the way down and/or back.
Certainly not the first choice when understanding what is needed for a cyclocross-racing parent. However, I hadn't got a clue what I was going to be facing when I bought it.