Calum, Lochter had some open water and was fishable on Sunday so there should be more open water by this weekend. As you might imagine if the whole of the lochs are not open it might be a bit crowded.
Similar story for Loch Insch at least two of the loch have open water I might give it a go this weekend.
I emailed them and they both gave prompt replies, try that as this will give the most up to date info.
Concur with Jim, my experience of Peterhead south harbour is a good place to sacrifice tackle to the sea gods. Fishing on inside of the harbour is not so bad, lots of bites but fish were on the small side (fish finger size). I fished up there in Sept so the fishing may be a bit different now.