I've been to Woodland Caribou Provincial Park, NNW from where your lake is (still Ontario) 5 times. I agree with the other posters. I've never had the black flies issue but I fish in late summer, the opposite of when you are going. I would stressed the 'be prepared' for any kind of weather; it changes quickly and often, not just day to day, but hours.
Here are some things I've picked up over the years.
1. Pack lightly and essentials only. It is all too easy to 'feel' the need for this and that.
2. Rubber boots - I bought cheap rubber boots from Walmart. Make sure they are sized correctly and use with heavy socks to reduce chafe.
3. No more than two rods; have an agreement with your fishing buddies to share if something breaks. Again, travel lightly. The fly-out weight limitations can be costly if overweight. Ok, 3 rods, but make them two piece, especially if you can portage to other lakes (not mentioned in post).
4. If you don't have indoor plumbing, but outhouse accommodations, bring wipes - you will thank me!
5. Your bass/crappie setups should be fine - bring rattle-traps. They are very effective on walleye and pike, silver with blue back being my go to. On sunny days be sure to use more silver and on cloudy days, gold (including rattle traps).
6. Worm harness tackle for Walleye. Goes without saying to bring worms if using. It's not necessary, but it is a good backup plan if fishing gets tough, and regardless of the wow stories heard from up north, fishing can get tough with fronts rolling in often.
7. The lakes I have fished had plenty of bottom rock structure. To save losing rattle traps, I replaced the trebles with double hooks from Barlow's
(not affiliated) by removing front/back trebles, adding another split ring to allow the double hook to run true. This allows the lure to glide over obstacles. I do this with spinner baits without the split ring. If you do get snagged, simply back up the boat beyond the snag and this will almost always unsnag the lure. I found my double hook setup to not diminish hook up rate.
8. Check to see if they furnish PFDs. Some outfitters do, some don't. If they don't, ask if they rent them. Rent if possible because that is less stuff to bring.
9. If you drink adult beverages, don't underestimate the amount you will quench your thirst while up there.
10. 10-20 lb. line should be plenty. I would take some fluorocarbon 8lbs for leaders if you find that fishing is finicky. But with those toothy species, good luck with that. Speaking of leaders, definitely get some metal leaders like used for saltwater fishing.
11. Don't underestimate spinner baits or spoons.
12. Understand the responsibilities for each for camp duties: cooking, fish cleaning, washing dishes, etc. Since this is your first time, your buddies probably already have this down. So ask what are expectations. You want this to be an enjoyable time, not some nit-picking disagreement.
13. Ask the outfitter to give you 6 names/contact info from others who have fished this lake. Call them to get fishing info. I have found this to be particularly informative. As a matter of fact, I just received a call this past week from someone who fishes the same lakes as I do as he was traveling in Texas to attend a family funeral. We've never met in person, but have been phone buddies for over 15 years.
14. One of my documented trips can be viewed at Canadian Fly-In
15. Bring a digital camera. I wouldn't rely on the phone camera only. You cannot take too many pictures.
16. I don't know if there are bears in your area, but I've had two incidences on separate trips, so read up on bears for what and what not to do.
I could go on and on. If you want to talk, just pm me and I will provide my phone number.
Have a safe and great fishing experience.