Most cycling holidays are rides with food attached. A training camp is a different thing. There is a plan, the days build on each other, and somebody is watching what you are doing and telling you when to back off.
This replicates a Tudor Pro Cycling camp. Team performance staff run the programme, team coaches and mechanics work on you and your bike, and team riders are in it rather than dropping by for a photograph.
Bike fitting on arrival. Structured days. Nutrition matched to the training. Massage and a debrief each evening.
Three days is the shape it usually takes, and it can be built around wherever suits your group.