In Minnesota does a father leagally have to provide clothes, diapers, etc. for children when he has them for visitation every other weekend or does the mother have to pack and send these things with the children?

NO, that is what he pays child support for.

You should send junior with enough clothes, medicine, toiletries (rash ointment, Baby wipes - Fill one of those travel packs for the diaper bag. More than enough for a weekend.)
And a few diapers. Tell dad he needs to buy a pack of diapers for the weekend.

But the rest you should send with dad.

Legally -that is up to the two of you to agree on for the most part. The Judge takes that into consideration when he sets child support that it includes where ever the kid goes. So mom SHOULD pack diapers.
Most mothers do pack up the diapers and have a wardrobe of clothes at the father's as well as at the mothers.

Correct, normally if the two of you can not agree, you go back to court and get it ordered though the court.

Normally yes, the father who is keeping the child will have their own diapers, some of their own clothes, toys, bed and everything the child will need.

Normally the mother will pack some clothes and diapers but the father in all cases I know of, always supplies most of his own.
They make sure to send back the clothes of the other when the child is exchanged.

It is for the child so if any supportive devices are needed for the child, you should send them. I send my daughter with whatever she needs and also what she wants to make her feel comfortable. I'm not doing it for her father, but for her well being. Good luck. Just remember the children.