That's all correct on the advise. I do have eggs due to hacth in 8 days now though, but up in Ontario they are probably right with it being later on. Most do lay BEST at 2 years on to 6-8, first years layers are luck in my experience, but they will do it on occation.
There is no big deal on pinioning. It needs to be done at a day old when possible, though I have pinioned adult birds too, just much harder on them then. They fly like no bodys business, so dont let them out if they arent, these arent "pet" ducks, they will leave you in a heart beat. The only draw back to pinioning is, they are now defenseless to preditors, so you still need to keep them in an aviary if you want them to be safe. So, for my persoanl birds, I always build large covered aviaries and enjoy watching them fly around. If you have a large pond for them, they'll have a better shot if pinioned and let out, but still, if you have bad critter problems in your area, they'll eventually disapear on you.
oh forgot, if your seller bought them at an auction, unless they were babies, he honestly has no idea how old they are!