no need for fertilizer - the native plants tend to not like fertilizer. some native plants are burned by fertilizers or they "over grow" turning into huge behemonths mutant plants that fall over...

I agree with joepye about about fertilizers.
When installing your new friends DO NOT let them dry out. That is the number one rule when planting anything. You live in the Chicago area same as me and we are still in the middle of a horrid drought. Make sure they have plenty of moisture till at least early summer next year. The mulch will be most useful in that task. After that natives can pretty much look after themselves.
There are natives that have evolved to live in damp soils such as Culver's root, Mallows, etc., I water those once and the while and plant them closest to the downspouts of the house.
Make sure the grasses have full-full sun and lots of room, perhaps 2 1/2-3 Ft. apart.

Thanks for the tips.