Curiously enough I have just been involved with supporting and helping an elderly friend who is doing an equity release.
First of all, if they do do it, then make absolutely sure that they have a reputable adviser and decent solicitor, as there are sharks out there, even though the market has been cleaned up a lot.
That being said, it can be a good thing for the elderly people, as it basically gives them access to wealth which they have accumulated but cannot use / enjoy, and so could buy them comfort and peace of mind. Personally - and it is only a personal view - I don't think it should ever be done to advance money to children, except perhaps in an emergency eg a medical emergency or something.
On the specifics, with a reputable company they do NOT give away or lose control of the property - it is actually just a mortgage, but with no repayments because interest is added to the amount outstanding. They cannot be forced to sell, but the loan will become repayable if either they do sell the property themselves, they die, or they move out permanently into eg a care home. The lender then has the right to sell the property and take the amount owning out of the proceeds, but no more than that, so there will always be a balance left, unless property prices collapse completely, because the lender will never advance the full value. A reputable scheme will also have negative equity protection ie if prices do collapse and the property is worth less than the outstanding loan when it comes to be paid off, then the balance is written off.
Hope that helps.