Too many cruisers are worried way too much about this. Anchoring in Lahaina is the best! But with the increased cruise ship traffic in recent yeras and the number of charter boats and ship tenders all vying for a minimal space at the only loading dock...plus new port security measures, it's not what it used to be. Ships are frequently changing to Kahului where you "walk" off the ship like any place else. Most cruise lines who are better organized, have free buses shuttling passengers to Lahaina anyway, from Kahului. It's about a 45 minute ride.
Get this... amazingly, you'll be bussed to Lahaina from Kahului, and be standing on Front Street shopping, long before you'll get ashore by tender in Lahaina...especially after standing in long lines waiting to get on the next tender.
Cruise lines are getting tired of passenger comlaints about the length of time to get ashore at Lahaina....that's why they are opting to go to Kahului instead. Stay with it and you won't regeret it.