Viking, based on your use, the 5W may just squeeze you by, but batteries tend to lose a little charge on their on, and if you are using it, or you dont get full sun and considering your Northern climate you will probably be averaging putting 2 amp-hrs per day into the battery. That,s not much, and even with the 15Watt panel, that is only 1 amp charge for 6-8 hrs., a good trickle rate. Either the 11 or 15 Watt would be good. You may even want to trickle your fish feeder battery if you have it close.
You will not need a charge controller, it can never overcharge at 1 amp rate. I would still give it a fast charge occasionally to knock the sulphate off the plates. Sorry for rambling, but not much else I can add in the way of advice to this forum.
Let us know how it works out.
