If it can be done legally, it seems a good idea, and property is a reasonably safe investment. But if you're going to do this:
Let's say the house costs £100K - £45K of yours, 25K of the kids' and 30K mortgage.
You would own 74.8%, and each child would own 8.4%.
You would pay the mortgage, as that's part of your share, and every month each child would receive 8.4% of a fair rent for the property, paid by you. That seems fair.
When the house needs insurance, repairs or maintenance (not redecorating) you could use their saved rent money to pay their share of the bill, so for a £100 repair bill, each child would pay £8.40 towards it.
When the first child reaches 18, you sell the house, whether you want to or not, and divvy up the money.
I think this would be fair to them, and a sensible use of the money, but it would need to be overseen by a solicitor (paid by you, since you and DH are the ones who benefit from this interest-free loan) and each child would need a charge on the house for their share.
Frankly, I wouldn't do it. It sounds far too complicated!