The first retreat we went on, we took five projects and finished none. The second time we took two and finished one. The difference was not discipline, it was packing for the knitter we actually are rather than the one we imagined on the drive there.
Two projects, chosen coldly
Take one simple project for the talking-and-knitting hours and one complicated project for the quiet ones. A plain sock and a lace shawl. Anything in between turns out to be the wrong one at the wrong moment, and you will spend the weekend resentful of both.
Do not take anything with a deadline. Retreats are the one place where a project without a purpose is the point, and a garment you must finish for a birthday will sit in the bag while you knit a dishcloth out of spite.
How to pack it
One bag per project, not one bag for everything. You will want to grab one and leave the room without repacking, and a single shared bag means an evening of untangling at the start of every session. A compact project bag for the sock, a standard one for the lace.
Then a small notions case with a spare set of needles in the sizes you are actually using. Retreat shops sell yarn, and there is always a skein that demands a different gauge than the one you packed. This is not a failure of planning, it is the entire economy of a retreat.
Needles, airports and security
Most countries allow knitting needles in hand luggage, and most security officers wave them through without comment. That said, policies vary and the decision is always the officer’s. Wooden and bamboo needles attract less attention than metal, circulars less than long straights, and a project already on the needles looks like a hobby rather than a threat.
Pack a self-addressed envelope with your least favourite needles if you want insurance, put scissors in checked luggage, and never argue at the tray. In fifteen years of flying with knitting, the worst outcome we have heard of is a confiscated pair of metal straights.
The actual point
A retreat is not for finishing things. Pack two projects you like, one bag each, a repair kit, and nothing you are obliged to complete. The knitting that happens on the third evening, when everyone has stopped performing, is the reason you went.