The government gives you money(low taxes)/buys something, and does so by borrowing the money for a long time. Now future generations (their children) are on the hook for the payments, having to pay higher taxes in the future for benefits in the present.

This is fine if you are using that money to invest smartly, such as in needed infrastructure. This is not good if you are doing it to lower taxes to win elections.

This is how you can "sell you children", though I prefer the more correct language of saddling them with debts.