"The reason for doing the passage at one shot is the lack of time"
I would second everything Tomaz has said but also add that this is also the time of the "Christmas Winds"...which are the heaviest winds and seas of the entire year...Conditions offshore of 25-30knots from the NORTH/NW are accompanied by impressive seas making passages between the islands difficult and dramamine a basic food group!
These conditions come and go for several months and people generally hunker down in harbors or sail in protected waters when they are active. What concerns me about your plans is that they are time bound and you can't sit and wait things out...and you may get there just fine then be faced with a return sail to the NW into the teeth of such conditions with no time to wait it out. On a cat...you'll get a new appreciation for the words "sea-kindly" .
I'm not saying you can't do the trip...but I would suggest you also make alternate plans and not be driven by the vacation clock in your decisions. Leave the boat and hire a captain to sail her back when conditions permit if you can't sail back yourselves in safety.