The trick to keeping sunfish with grass or redfin pickerel is to keep many fish together.One or two sunfish won't work well.You have to have several tank mates. They all don't have to be sunfish. They can be anything that won't fit in the pickerels mouth and vice versa. Also another important factor is you have to keep everything very well fed. And you have to feed enough to allow the pickerel to compete.
I have personally kept green sunfish,pumkinseeds,warmouth,rock bass,longear sunfish,redear sunfish,bullheads,crappie,carp,and large chubs with both redfin and grass pickerel several times. The only time I had any issues was with a large green sunfish that harassed the pickerel for about 3 days. At which point the pickerel must of had enough. When the green sunfish grab it's tail the pickerel turn and nailed it on the head(actually grab ahold of it). The green sunfish had a mouth size wound on it,but it never bothered the two pickerel again. And they were housed together for 3 years.
It's not impossible,but it requires the right conditions and a lot of food.Also make sure the sunfish are a least half the length of the pickerel and any chubs or suckers be about the same length or larger than the pickerel.