Do it room by room, obviously depending on what space you have in the car.
Work on the assumption that you may not come back for a long time, just in case.
Bathroom: your special toiletries and make up. Medicines. Don't bother taking things like cheap shampoo and soap, because you can buy fresh as needed: the space in your car may be better used for other things.
Child's bedroom: clothes, but not ones they are growing out of or will have grown out of come Autumn/Winter. Favourite books and toys. If they have a favourite duvet cover take that.
Your bedroom: your more expensive clothes, and a few cheap clothes. You can get more of cheap things like leggings and t-shirts. Check: Top half: tees, tops, jacket or coat, warm hoodie or jumper, Bottom half: skirts, jeans, leggings, Other: underwear, socks, footwear, nightwear.
Sitting room: electronics and chargers (phone, laptop, whatever tech you have, maybe the TV if it is expensive?) Any favourite items for hobbies or sports. A favourite throw or cushion. Any favourite ornaments. Photos.
Kitchen: any favourite small tools or small bits of equipment that you love. e.g. I have the perfect can opener and potato peeler, and I would not want to have to replace them.