I don't have much experience with the 4 fishing lakes but I do know that the largest walleye seem to be come from Katepawa lake,{the farthest lake to the east}. Perch can be found though out the 4 lakes. I would be very very cautious on these lakes yet, they have some current in them and ice can be very very thin at times. I was out on Katepawa 2 years ago and most of the ice was foot and a half thick, I went a few feet close to shore by a point and it was only 6 inches. Use EXTREAM caution on any lake but particularly on them. Last time I was in the Fort Qu'Appelle the river was still open.
Contact the Fort Qu'Appelle SERM office, I am sure they could help you on the fishing and ice conditions.
Good luck and stay safe.
WW