Hi Tom
You are correct to identify the problem as relating to how repeatable field groups are stored.
They are implemented via child posts and each field belongs to the child post rather than the parent directly.
To illustrate, let's use an example with an Offices repeatable group of fields, that has individual fields for Phone, Email, Manager, and City.
Custom fields are stored in wp_postmeta and always belong to a specific post.
We add several Offices groups to our Acme, Inc post, filling in details for each of the fields.
So, in wp_postmeta, attached to the Acme, Inc post we have several phone numbers, several email addresses, managers, and cities. But nothing to connect a particular phone number to the associated email address, manager, and city, they are mixed up. (We'd essentially need an extra column in the table to group the field entries.)
The Toolset solution is to store each group of fields against a child post of the Acme, Inc post. As many child posts are added as groups of fields are added, one for each Office in our example. That means the fields like phone and email address belong to the child office post, not to the original Acme, Inc post.
That's why you would use a View to output the repeatable groups of fields belonging to the Acme, Inc post, for example, where the View actually queries the child post type.
And so the problem in your case is that you cannot filter one post type by the properties of another.
If you are only filtering by date then you could use a View which queries the child RFG posts, because in the output of the View you can output fields of the parent Tour posts (so a Tour title linking to the Tour post, for example).
But if you were also filtering by other fields or taxonomies of Tours then you would need the View to be querying the Tour post type, in which case you would need date fields (or terms) that belonged directly to the Tour posts to be able to filter by them. To improve the experience for your users you would likely want to use some code to automate that, so that when a post with date RFG fields was saved, they were duplicated in some way on the Tour post itself.
