Solicitor will charge an arm and a leg (if not two arms, two legs and most of the torso) to manage a POA.
A POA is a very personal thing. There are two kinds now and one for Health and Welfare, which should definitely be held by someone who knows you well enough to know what foods you do not like for example (if you go into a care home) and one for financial affairs. Here is a link to a helpful government site explaining it all. www.gov.uk/power-of-attorney/overview.
Use a solicitor to set the POAs up. You could make a solicitor and a DC your Financial POA, with your DC making the decisions with advice from the solicitor. Running a POA is actually not a lot different from running your normal bank account.
When I looked after an uncle, I would do any bits of shopping he needed; clothing, toiletries, books, CDs etc. I just took £50 - £100 out of his account, kept in a separate purse, bought from this purse, what he needed and kept the receipts in a file.
It is a bit of a palaver to have to go to a solicitor every time one of your parents wants a bar of chocolate or wants a particular brand of underwear or nightwear.