I am planning a week-long trip with my cousin, June 1-7. We want to bring minnows up (5-8 dozen). is the best way to keep them just in an oxygenated bag and haul them in a bucket and then transport them to a minnow keep once our destination is reached?

Probably. Consider having your oxygen bag inflated inside a Bait King. Pretty handy in camp and much more critter-proof than other buckets.

Leeches might be hardier (I'd use the same procedure), but that wasn't your question, was it?

Suggestion: Unless you are in the BWCA with a motor permit and have a boat with an aerator, skip the live minnows in June. Bring some packs of Gulp 4" minnows and some 1/4 oz jigs, a lot lighter and easier. Add some other plastics and a few hardbaits and you have it made. If you want to do some lazy, relaxing slip bobber time, Schweady is spot on regarding leeches.

Read a hack the other day. Said put half cap hydrogen peroxide in bucket to increase oxygen.. I'm thinking no way. Should have kept that. Cause I didn't believe it.. might have to go get a few minners from buddies bait shop. Just to see it it kills them.

I’ve humped then in, in a minnow bucket dipping and changing water at each stop. But I was only bringing 2-3 dozen, not 5-8. Not sure if that is feasible without changing water and a 5 gallon bucket of water would seem to be kinda tough to portage. You didn’t say what kinda trip you’re planning. If it’s only a couple portages it might work.