Hi Gunilla, I’d suggest using a cart and walking on the Langdale ferry with your kayak. At the other end, roll up to the bus loop then turn sharp right into the parking lot and find the start of the beach trail immediately to the right. The trail has been improved and there is a lovely sheltered sand beach to launch off.
This would be a reliable and lower-risk way to get to where you are going. The crossing to Gambier is 1 NM. Your destination is only about 1.5 NM beyond that, from what I can tell on your map, so about 1 hr total from your launch.
Parking at HSB is the disadvantage of this route, but Lions Bay parking is as bad or worse and a much longer and more serious paddle.
I don’t recommend that you paddle alone, but if this is something you are used to doing and you take all the standard precautions, it is what I’d do without hesitation.