(not for ever, but for this week) call on your friends and their partners and your neighbours for 'garden support'. In your situation so many people will want to do something to help, but will not know what to do. So ask them. (bring petunias, bring sunflowers, bring vibrant geraniums in pots). On Friday have a big garden party where you and your dc celebrate your space and make it look fabulous.
Use the help of friends and neighbours to get the lawn mown and watered (it's going to be hot and dry this week), edges strimmed, planters overflowing with bright and beautiful flowers - especially the front garden / approach to your house... (I'm thinking a Chelsea Flower Show vibe). Buy whatever you can.
Involve your dc in the 'gorgeous garden project'.
So when exh turns up on Saturday, there is not a 'sad' bedraggled garden with overgrown plants, instead an F You riot of colour and abundance and joy. Send a garden message that you don't need him to 'help' with the grass, show how you are all flourishing without him.
Maybe seed the lawn with poppies spelling out There We Are Then...