Increasing rent notification and lease modification

[Brian S.]

The two year lease on our first SFR is up at the end of May and I have a couple of questions for anyone willing to give some feedback.

The lease states we may increase rent upon 30 days notice after the initial lease term.  There is also an addendum which states the lease will automatically renew year to year unless one party gives the other 60 days notice.  We are planning a modest increase in rent.  Any thoughts on the preferred method of delivering this notice to ensure we have proof it was received?  Is there a standard form or letter you have used in the past?   Should we have them sign something acknowledging the increase in rent?  If so, what are some recommended ways of doing that? 

In the event they wish to go month to month or renew multi-year as opposed to the automatic one year renewal in the lease, should we execute a brand new lease or is it better to do a modification / addendum of sorts to the existing lease simply outlining everything is still in full force and effect and we are simply changing the length of the lease?  What is the best way to do this?  Does anyone have a resource for forms / letters etc. that might be helpful in this situation.

Not sure if it matters but the home is in St. Louis County, MO

Thanks!