What I understand from your scenario is that you will have two entities Reservation and Attendee with a 1-* many relation that means there could be many attendees on a single reservation. So setup the domain model, and then on the page where you have Reservation data view to show the reservation, you can nest inside that data view any other listing widget like list view or grids and use the association to show all attendees details here.
Please check the academy learning paths. There is a good example about implementing training events and trainees.
Thanks for that, however now when inserting data, the actual value of the attributes are shown right after you have inserted them. When I insert another value, the old values seem to disappear and only the new value is shown, as you can see here below: