The attendance allowance forms can be done online or on paper. Get the paper version.
Partly because the online version is an absolute nightmare to fill in - very badly set up. But mainly because if you use the paper version payments will be backdated to the date you requested the form, whereas with the online version they only backdate to when you submit the form.
As for the money disappearing, you will be spending a big chunk of it either way. All annuities are an actuarial gamble, and the firms selling them have professional actuaries - so they are more likely to 'win' the financial bet of whether you pay them more for the annuities or they pay you more for the care.
However, the stakes on your side aren't just financial. There's also the value of certainty.
How do you balance the high probability of an annuity costing you a bit more but giving you guaranteed set payments for as long as needed, against the low probablilty of direct payments costing you a lot more, and the very low probability of running out and having to deal with unwanted care home moves for someone by then in their 90s?
Everyone has their own circumstances and risk tolerance, so you'll need to decide that for yourselves once you have a quote and a better idea of prognosis.