Wisconsin - No lease agreement in place

[Tracie Van]

We took over some duplexes and I noticed that one person's lease ended May 31st of this year. I don't want to renew them for a year. I'd like to just give them 28 day notice, but its unclear if the lease automatically converts to month-to-month. 

Lease says: An Agreement for a fixed term expires without further

notice. If tenancy is to be continued beyond this term, parties

should make arrangements for this in advance of the expiration.

No written notice is required to terminate a lease for term because the lease automatically ends on the last day of the term. Nonetheless, both Landlord and Tenant should discuss prior to the end of the original lease term whether or not they wish to continue the tenancy beyond the original lease term and if so, enter into a new rental agreement accordingly. Month to Month Tenancy – Written notice must be received by the other party at least twenty-eight (28) days prior to the ending of a month to month tenancy. A month to month tenancy may only be terminated at the end of the rental period. 

What is best option? Inform them that their lease ended on May 31st, (to show that I 'discussed' this with them) and that the lease will convert to month-to-month, then after 30 days pass, serve them the 28 day notice? 

Or can I just serve them the 30 day notice?