Make use of swaps into LN or liquid.

For example: If you need to spend on chain BTC 500k sats with a 200k, and a 100k change, line up that change into a swap (bolts/robosats) for LN or liquid.

This way you're able to spend on a second layer for smaller purchases.

As for your DCA, you need to set a higher limit for withdrawal. Say more than 1m sats.

And your kids should be receiving their allowance via LN. When they have saved a larger amount (over 1m sats) they can transfer on chain if its worth doing.