Being flexible is key, if you see a window of opportunity you can take it. It's also good to have flexibility in the time you allow for the journey, that way the pressure is off on arrival date and in the event of poor weather conditions you can simply sit it out somewhere warm and cosy ! You should be thinking 5 days minimum for the travel, 7 days would give you time for a little sightseeing and/or 'wiggle' room for the weather if needed, plus sometime enjoying the outdoors with the pup.