I don't have time for a lengthy reply right now, but I always viewed the plan as Luke getting everyone inside Jabba's palace so a rescue effort would be easier. By getting everyone inside, he forced Jabba to leave the palace and go to the Sarlacc pit. Without getting Han out of the carbonite and killing the rancor, thereby REALLY pissing Jabba off, there was no way to get Jabba to leave the palace. Once he was outside, the rescue effort was going to be relatively painless and they'd be able to destroy Jabba's sailbarge at the same time.

It's far easier to take someone out when they're outside, relatively unprotected, than when they're inside their own palace, surrounded by their own people.