Why not cook a meal together, something completely different to what you might usually have? Go a little out of your comfort zone, culinary wise. Discuss it together, aim to choose something you have never eaten and/or cooked before (or a new style of global cuisine).
Discuss it to choose something together, get the ingredients together then work as a team to prepare it. Have a few cheeky drinks during it. See how it turns out - even if its minging, you will still have been talking, spending time and hopefully having a bit of a laugh together.
If confident, even try for a dessert too!
Set up a nice, fancy, candlelit table to enjoy it together when ready.
Or why not see what activities there are near the cottage and again look to try something new together. Maybe something outdoorsy or adventurous. Rock climbing, surfing, orienteering, sailing etc.
Or take some art supplies and take a shot at being a life model for each other, at the cottage. Pose nude to up the ante! Set a time limit for each's drawing, so it doesn't get ridiculous - but don't be insulted if the outcome is not flattering lol
Or what did you used to do together when dating?
Dont put pressure on yourself / each other to "must have amazing fun" (its not a hen do). Its OK to still take some time to relax and give each other space.