I want to set up a single admin login that all my club users can access

In a word - DON'T!!!

It is just about the most dangerous thing that you can do on play-cricket. If people need to make updates, they must have internet access. They must therefore be able to create their own username and password and have admin rights granted to that login, rather than having a 'generic' one, which is fraught with dangers. What you would be potentially doing is giving access to all of the sensitive personal data on your club's site to any number of people without knowing anything about them. At best you might get away with it; at worst you could end up in very serious trouble to do with safeguarding and data protection legislation.

For example, what do you do if you no longer wish a person to whom you have given these 'generic' details to have any admin access? You then must change the login details, and try to notify everyone else who you think might have access of that change.

What do you do if someone amends the login details, accidentally or otherwise, and locks out everyone else who was using the login?

How do you control who else these details might find their way on to when everyone knows them?

How do you know which individual might have made changes in the audit trails of results and scorecards?

Logins like this are notorious for being passed on to other people without your knowledge. People also tend to treat their own login details much more carefully than a 'catch-all' such as logins like this