There is no shortage of things to do in Vegas! Gamblers and non-gamblers both will have plenty to choose from! Here's a site with some of the current events/attractions around the city:
And here's a link to the Weather Channel site for Las Vegas. We're still too far away for a precise forecast, but it looks like the averages for mid-May are 90 during the day and upper 60s overnight!
http://www.weather.com/weather/today/Las+Vegas+NV+USNV0049:1:US