Throughout the year there are organized road trips, rallies and motoring challenges in various countries. Some are short, some are long. Some have higher entrance fees depending on what is covered. Some are for personal motivation, others for specific charity fundraising.
Peruse the list and see what takes your fancy. Most of them are annual events and as you need at least one to two years to prepare yourselves, co-driver and your vehicle for a major motoring challenge, you have time to research the relevant website and the entry details. More events will be added as they come to hand. Also check out your local car clubs and motoring magazines.