3 xboxes, 5 kids, 7 players...

Wow! A gamer family? That's nice! If you have 3 xbox one consoles, you don't need to buy more than 2 subscriptions on both. Like the others friends said in the comments section, you have the option to share the live gold accounts in the 3 consoles.

Here's a article that explain everything that you have to know:

https://support.xbox.com/en-US/xbox-one/xbox-live/xbox-live-gold-sharing-features

Have fun, bro!

I can relate, as a family of 5 and having to buy multiple subscriptions. It would be nice to have the Family Gold as there was a couple years ago. Unfortunately, it would possibly be abused in some way and therefor wont happen.

Smwutches explained the cheapest viable option for the current situation.

It should be noted that the console licenses transfer can only done once a year a believe

Hello,

You can turn on the console on to Family Console. So everyone on that xbox has gold when they play.

This has been answered with the sharing links, but I would also add that you should try the Microsoft rewards program. We are a three gaming console household and I have Ultimate covered for the next couple years through rewards points. I earn points via
browser searches, mobile searches, Xbox/Gamepass App and regular Microsoft/Xbox purchases. Even if it covers one of your gold accounts, it would probably be worth it. I estimate it takes me about 30 min a day to get through my points earning activities, but
I work from home so it might be easier for me than most. I should also add, I am in the US and I'm guessing you might be AU, but the rewards program should still work there. Honestly, its pretty decent rewards program and I've been really happy with it.