It's not clear why you've been given the advice. If your sons are still children it might be because the Government's Child Trust Funds were a good way of saving for children. However they've now been replaced by Junior ISAs, so the advice you've been given is out of date and its Junior ISAs that you need to find out about:
https://www.moneyadviceservice.org.uk/en/articles/junior-isas
Or have you been given the advice as a suggested way of avoiding Inheritance Tax? If so, you need to know that there's no IHT to pay anyway if your estate is worth less than £325,000 (or £650,000 if your spouse predeceases you and leaves everything to you). Otherwise this is a good place to start:
https://www.moneyadviceservice.org.uk/en/articles/using-a-trust-to-cut-your-inheritance-tax
If you have a considerable sum ( say £100,000 ) which you can set aside, and if you are liable for inheritance tax, this sum would be removed from the taxable total of your estate if you set up a trust fund for your sons. However, you Really Really do need advice, and you will have to pay for it. You may be able to get a list of financial advisers and their specialisations from the citizens' advice bureau.