They are crossbreds, and very pretty "love the color of the gray ones". They all look to have a little bit of Sebastopol in them. One has a little crest so it's likely got some Tufted Roman in it. May be Pilgrim crosses...I'm not sure if the auto sexing carries into second generation.
Age is tough to tell with geese. They are obviously not babies of course. They don't look "old" to me, I'd say they are around 1-3 years old.
Sexing mature geese is very easy buy vent sexing them. Hold the goose upside-down in you lap with its tail facing away from you "put the head under you legs to prevent biting your arms". Gently press around the vent with both hands. Fingers on top and thumbs bottom, so that you are pressing all the way around the vent. You may have to manipulate the vent a little as well. If its a male the "reproductive organ" will pop out, looks like a furry corkscrew. If nothing, its a girl.