We're currently in an unsteady pattern of hot/cold/storm/dry, which is not strange for June. Watch the weather forecast and plan for the worst - 1 warmer layer and rain gear in addition to your shorts & flops. A tarp wouldn't be a bad idea also - a makeshift group shelter or protection for all your gear. Also bring lots of sunscreen & bug juice. Walker is likely cooler than the cities, but the sun & bugswill still be strong.
There's a great casino in Walker with live acts, and I know it's popular with guys weekends for golfing & fishing. You're also not far from one of the best state parks - Itasca. If you have time, spend a day there hiking, swimming, biking, canoeing. Visit the headwaters, where the Mississippi River starts. Have some pie & coffee at the historic lodge there.