You can just add a Custom Link menu item and link it to #. A better UX though would be to have a Page called Activities that simply acts as an index with links to the sub-entries.
Thank you for your help. For me it is strange the difference between Page and Post. In joomla there is not such difference. There is just the concept of article. As far as I have read, post is for blog and you can categorize and pages is for “static” articles.
I will try your porpuse.
You have read about the theoretical intent of posts and pages, but the reality is quite different. Forget what you’ve read 🙂 Nearly all site content is a post of some sort. “Post” as in post_type. Then there is the post post_type, intended for blogging, but could be used for any purpose if blogging is not part of your site’s scheme. What makes pages unique is the fact one can specify a specific template be used for every page. This is very powerful as far as customizing WP goes. A page template can do anything that’s possible with PHP, which is quite extensive. Because of this, pages can be far from static.
The other major difference is pages are hierarchical, posts are not. But since one could create their own custom post_type, it doesn’t matter what pages and post post_types were meant for, you can create your own post_type to fit your specific needs. Unfortunately, both post and page are very ambiguous terms, so confusion is inevitable.