How to exclude a page from the navigation tree
Use a descendantOf parameter with a new ElementCriteriaModel instead of the getDescendants method on your entry model and you can add additional parameters. In your case add cf_hideFromNav as a parameter:

{% set topEntry = craft.entries.section('pages').slug('club').first() %}
{% set navItems = craft.entries.section('pages').descendantOf(topEntry).cf_hideFromNav('0') %}

{% nav navItem in navItems %}
    ...
{% endnav %}


You could also use the parameters id or slug to exclude certain entries:

{% set topEntry = craft.entries.section('pages').slug('club').first() %}
{% set navItems = craft.entries.section('pages').descendantOf(topEntry).id('and, not 23, not 40, not 12') %}


The descendantOf parameter also takes IDs. This would allow you to do this all with just a single ElementCriteriaModel:

{% set navItems = craft.entries.section('pages').descendantOf('1').id('and, not 23, not 40, not 12') %}