You should be able to find walleye action on wingdams in mid-July. We have been doing very well on walleyes up here since mid-April with lots of 20″ plus (protected fish) making it to the boat. Even with all the fish over 20″ there are still lots of eaters to be had. I’ve been getting fish casting crankbaits over wingdams and fishing the dams with 3-way Dubuque rigs tipped with crawlers. As the month of July wears by the wingdam bite slows. The fish are still on the dams but there is just so much food in the river for them by then that they can be very picky as to what they want to eat. I have found the fish to cooperate the best in the early mornings and again in the evenings come mid to late July. Concentrate on the wingdams and closing dams with the most current. Fish the insides of dams in the mornings but work out to the channel ends during the warmest time of the day.
I am afraid I won’t be a whole lot of help on the crappies. I did spend a half day this past weekend targeting crappies on deep snags in a slough with some current (but not much). We were able to get a couple crappies on tiny jigs but had we had minnows I think we could have done much better. We were using tiny Roadrunners and sparkle jigs. I would advise whatever you use to be weedless if you want to fish snags. I found that chasing crappies is too-much work compared to walleye fishing.
Best of luck!
Eyehunter