Resellers like Viator and GetYourGuide are good at one thing: putting your tour in front of travellers who are planning a trip and have never heard of you. They charge for it - GetYourGuide's supplier terms describe its commission as "a percentage of the Retail Price for a Booking, as specified in the Supplier Account", so your rate is in your own agreement.
Keep them for that job. The question is how to sell the same departures on your own site without selling a seat twice.
Option 1: connect everything to one availability
A booking system connected to your resellers updates every channel when a seat sells anywhere. It is the right answer when resellers are a large share of your bookings and the numbers change daily.
Option 2: split the seats
Decide how many seats on each departure each channel can sell. For example, a 12-seat tour: 4 for resellers, 8 for your own site. Set a release time - say 48 hours before departure - after which unsold reseller seats go back to your own site. It is simple, and it works well when resellers are a smaller share.
Private tours and charters
One boat, one group. Whichever channel sells it first, block the whole departure everywhere, straight away.
How to choose
- Resellers are most of your bookings: stay connected through your booking system.
- Resellers are a small share: split the seats, or move everything to your own site and list on resellers through it.
- Not sure: count last season's bookings by channel. The split answers the question.