CORRECTION - EVENT INVITES is the Join Table!
You've put your finger on the problem. Currently, there is no data in Contributions that earmarks it for any specific event. If you had an Event ID field in contributions, then you could link up your records to Event_Invites by Event and Contributor ID fields.
Thanks... It occured to me that I would need to probably work out a method to connect each contribution to an event. The problem with that logic for me is that I need on the report I don't need to see each individual contribution per contact but rather their total in a given season.
Question about your response:
Did you mean that the relationship between Event_Invites should be connected to a TO of Contibutions (like ContributionsByEvent) using a new event_ID field and the contact_ID field? Would this help acheive my goal?
Once you have an EventID for each contribution, you can use a relationshiop to get the total contributions for a given invitee for a given event.
A total for a given contact of all their contributions for the season is possible without the eventID field--but I wonder how that total will work with your report. I suppose it would make sense though if your report lists all the events of the season for each invitee. A calculation field, cEventSeason can be added to Event_Invites that just copies this value from events.
Then this relationship
Event_Invites::contact_id = Contributions|EventSeason::Contact_id AND
Event_Invites::cEventSeason = Contributions|EventSeason::Season
will match a given record to all the contributions made by that contact for the event's season.