Have them sort change, and eventually to count it. It teaches them to gather things that are alike, it's an introduction to money and it occupies them for 15 minutes! Just make sure they're old enough to be past the point of putting coins in their mouth.
That uneasy, uncomfortable or even downright painful feeling you get when you’re faced with something that challenges you ... resist the urge to run away from it. Take a breath and just sit with it for a minute. That feeling you’re feeling is growth. Growth always hurts a little bit. Give yourself a beat to get adjusted before you decide if you want to stay or turn back.
Great article on making math fun:
https://www.washingtonpost.com/lifestyle/how-to-get-reluctant-children-to-embrace-math/2014/03/04/4be99e46-959d-11e3-8461-8a24c7bf0653_story.html
The next world is perfect and permanent. This world is neither, so save yourself the stress of trying to make things perfect (house, job, body, relationships, bank account, etc.) Embrace the impermanence by cherishing the good times. Know that the bad times won’t last. Remember that you are loved very much, and that God will shower you with the grace you need to handle whatever this imperfect life throws at you.
My Nana, born around 1913, used to decry “some people think the world owes them a living.” A hundred years later I agree. Nothing worse than entitlement.
Check out fencing. Local fencing club has classes for kids and adults all ages. They also do birthday parties, so that might be something different that would be fun for him and his friends.
Try silence. Just sit with it (problem/feeling/etc.) invite the problem to sit next to you and just be quiet. Five minutes every day for a week or two. Your solution will appear. Stop running and just sit with it.
Okay algebra and geometry but other than that, spend time practicing addition and subtraction, multiplication and division. That’s 99% of the math you’ll need to know if you’re not going to be an engineer, etc.
Sometimes you just have to let go. Let go of a relationship, or a dream, or plans. Let go of a person, a pet, or an object. It's hard. It takes a lot of trust.
Trust the Lord will heal the wound, no matter how deep. His goodness is infinite.