Hi OP,
I'm a will writer and never ask clients to appoint me as an executor unless they literally have no one in the world to act for them. This is because it costs a lot to have a professional executor and in simple cases such as yours there is no need.
I worked for 25 years in high street solicitors practices and we were always pressured to get the clients to appoint the firm as executors as they can charge a lot of money to do the work which frankly isn't rocket science. I see what you say about two executors at different ends of the country finding it difficult to co-ordinate and suggest that you either use a married couple instead as executors, or still use two sep. people but they can always hire a solicitor just to do odd bits of work if they're struggling (this is inherent in the will, or should be).
You suggest that the solicitors currently acting as executors don't have to write to 26 people but unfortunately they are under an obligation to notify each beneficiary individually.
In your case, I'd suggest that you just appoint two lay people to act. All they have to do is sell your assets, pay any debts and then send cheques out to your beneficiaries.
I do wonder, though, whether some of your beneficiaries are children whose parents are still alive (because there are so many of them!)
So if currently you have 5 beneficiaries, Mr and Mrs X and their three children a, b and c, it may be simpler just to pare that down to a gift to Mr OR Mrs X on the basis that the family as a whole will benefit. Otherwise the gifts to the children will be held in trust until their 18th or 21st birthdays, and unless these are large gifts they may be a bit of a pain to administer.
I have a paid for advert over on Classified Small Business of Mumsnet titled 5* Will Writing Service recommended by Mumsnetters if you're interested.