Your lake looks big enough to me! I like going out on little lakes every now and then. The big lakes like Lake Ontario near me, or Lake Michigan, near you allow for bigger and more consistent wind.
The nice thing about these boats is that you can enjoy them on small lakes like other small boat sailors do with their sailboats, but you also have the option to take them out on bigger lakes and oceans, and there aren't many small boats that can do that.
Here is a picture of me sailing on a smaller lake this past summer. The picture was taken from shore, and you can see the opposite shore on the other side. I had all kinds of fun on that little lake.

As far as your lake being too cold. Dress for the weather, but I haven't had any problems. I sailed in October in Canada. I've kayaked in the very early spring on our Revolution. There doesn't seem to be anything limiting the boat from sailing in cold water, it's just up to you to be safe.