For better weather, mid May, through the first week of Sept, generally are better than early May and 2nd 3ed week of Sept- which the later, has the worse potential for weather of the entire season. With the addition of dusk by 7pm, so port times and scenic sailing is cut.
Most tours are still running in this timeframe, with the above not accurate.
The longer cruises are repo, can be good deals. But if you have 14 days, a split land and cruise certainly offers you plenty in Alaska. Do your homework, head to your library and take out Alaska travel books, and Alaska By Cruiseship.
IF you go with a cruisetour- be CERTAIN you know and understand, fully everything about it. Most people do not. It is also simple and superior for seeing and doing more to go independent.