I don't understand your second paragraph, I'm afraid.
Without understanding your husband's precise pension arrangements and the amount he'd be sacrificing it's difficult to advise you, but if it's a defined benefit scheme then yes, the proposed arrangement MAY represent short term gain in exchange for long term pain.
Let's say he earns £50k and sacrifices £10k per year for both children's school fees. You'd save 40%, or £4k, representing the income tax, at his marginal rate, that he would have paid. However, he'd be assessed on a benefit in kind of £1,500 (15% of £10k), representing the marginal cost of provision. He'll pay 40% tax on that, i.e. £600. Total tax saving per year is £4k - £600, i.e. £3,400.
Now think about the pension. Let's say it's a career average scheme based on 1/60. By reducing his pensionable salary by £10k, he reduces the amount payable to him, post retirement, every year until he dies (morbid, sorry) by £167 for every year he does the salary sacrifice (£10k/60).
Over 7 years, that's £1,167 of annual pension income, every year, foregone. If he lives for 25 years post retirement, as many people do, that's more than £29k, at today's prices (the comparison isn't skewed by future inflation; public sector pensions are index linked).
His pension income will be taxed. Let's assume that he'll be paying basic rate on it, 20%, since most people's retirement income is lower than their income when they were working. He'd get his personal allowance of £10k in today's money, so he may not pay tax on all of it.
So you could save £3,400 over 7 years now - £24k - in exchange for sacrificing £29k, pre-tax, in the future, presuming that he lives 25 years. So in this example it might be worth doing.
Obviously, the numbers will be different in your case. I suggest you run the same calculation against your husband's actual salary, pension accrual rate and amount sacrificed. If the pensions accrual rate is better than 1/60, the salary sacrifice becomes worse value. The civil service's NUVOS scheme has a 1/42.5 accrual rate, for example; anybody in that would need to think carefully about entering into a significant salary sacrifice arrangement.