Welcome to BYC.
Expect mating/laying to occur when the ducks are getting near six months of age. This may come later with the geese perhaps early next spring.
Sexing most geese by appearance is unreliable. Characteristics such as lobe length, posture, sound, weight, temperament can be used, but, in my experience can lead to false assumptions unless experienced with the specific breed.
An experienced poultry keeper may be able to vent sex them for you, otherwise you will have to wait till till they lay or not.
A ratio of one male duck per six females is recommend to prevent over-mating, and damage to the hens.
Glad to meet you. What wonderful photos of your beautiful birds! Best wishes with the flock! I hope you an answer all your questions - use the duck and goose forums to get to the most knowledgeable folks on your topic - we who are greeting folks are a mixed bag.