My family is leaving 5/21 from DTW in the United States to travel to Venice to board a cruise ship the afternoon of 5/23. We are considering booking a Lufthansa two stop flight from DTW to Munich that only has a 40 minute layover to catch the next flight to Venice. Is 40 minutes enough time to make the flight to Venice? What else should we be considering as we plan for this first stop in Munich?
40 minutes would be very tight for this connection. Munich is your first port of entry into the Schengen area so you will need to go through immigration control in Munich. Depending on your citizenship and time of day, that can take some extra time.
If Lufthansa is willing to sell you this as a single ticket, it's a legal connection an you have a decent chance of making it. But there is no room for error: if anything goes wrong, is delayed or just a little longer than usual, you will miss it. If you do miss it, LH will rebook you on the next available flight for free, but you may miss your cruise, so I would advice against this.
There is NO WAY you can make this with two separate tickets.