Late june might be a good time to go this year, with things being a couple of weeks behind. I don't know if the thunderbugs will have crawled out by then or not, most likely they will have. If they haven't, use them. We used them for the 15 years that we went up in the middle of June and they always worked better than worms or leeches. Leeches were second best without question. There's a chance that the bugs will crawl out a few days before you get there, that always makes for slow fishing the first half of the week because the fish are already full of them and won't bite. If the perch aren't biting, the northern always are, so you would probably be further ahead to cast for them. It's a lot of fun.
One thing we found out around our 5th year going up was that the best fishing was casting along weed edges at night for walleye. Wish we had known that sooner, a half an hour either way of dusk is awesome. Year after year we nailed the walleye. We always used #7 floating rapalas, either fire tiger or perch seemed to work the best, just a mid-paced retrieve with the occasional twitch.