Love this - the possibilities are all so hopeful, congratulations on your rise.
How old are your children?
I think I'd do a combination.... Gym, cleaner overpayment and savings.
I think I'd go for the gym with nice pool assuming you could take the children AND also assuming you'd actually have time to go and would do so?
Meal boxes for me are more aggro, I never fancy what I'm meant to be eating or something happens that makes me late home and I don't want to or cannot cook so it ends up wasted.
I do have a cleaner, she is worth her weight in gold in the time it frees up. I don't work all week to clean my house all weekend, I want to enjoy my family then. She only comes once a fortnight so not too costly each month but makes such a difference and encouraged me to tidy/organise. Id do this too.
Id also do a small overpayment and small savings top up - one extra .monthly payment per year makes a huge difference (there's a calculator on MSE) os one payment divided by 12 so little extra each month.
After the gym, cleaner, overpayments what is left? I'd either I'd do a monthly takeaway/movie night style treat or if a bit more I'd do savings top up.
First though, id spend the first increase on a few nice treats for you and the kids - something you couldn't do before that would be appreciated by you all. Enjoy!!!