Yes, you can transfer AMEX points to Air Canada and book the same flights you can with United. However, most flights other than those operated by United or USAir will incur surcharges. United, Air Canada, AA, Alaska, Air France (another AMEX transfer partner) and others allow one-way redemptions, so you can use one airline or alliance in each direction. Another possibility would be to get one ticket with your UA miles and buy a matching revenue ticket. Having a better idea of your possible origin and destination airports would help as well.

I took my family to Europe in November (Thanksgiving) and while it was chilly, we had nearly everything to ourselves and never had any type of lines or crowds.