Commercial Space Port

Ah poo.

Chances are I'll have croaked by then

"Awwww, somebody got me mustard for my birthday..."

I'm not sure about in 20 years, or in 50 years. A more realistic estimate might be 100 years, since in order to travel to the moon, an infrastructure and habitat must be made available and stabilized, and at least somewhat self-sufficient before something as demanding as tourism would be possible. Also, remember that the spacecraft will have to handle the radiation that exists beyond the magnetic belts, and the astronauts who went to the moon in the past got a healthy dose of it.

Well, short term-trips (like the Apollo missions were) would be no problem, but staying there long-term might be a problem and would hence would require extra-shielding (i figure a moon base would be largely located undergound then). Although, things in general ain't that bad outside the magnetic belt (unless there's currently a solar eruption) - the radiation levels are usually higher inside the VanAllen belt itself (at least to my knowledge). But, normally you won't spend more time than a few minutes inside the belt (at least the Apollo astronauts did that on their trip to the moon).

The real trouble comes once we decide to visit Jupiter's moons. I'm not sure how far it extends, but Jupiter radiation field would be definitly lethal to humans.

By the time we're able to make trips out that far, there should be some sort of system in place on spacecraft that would block off most radiation, either with some sort of material on the hull of the craft, or energy emitted that would break up the radiation (anything could be discovered within the next few decades)

Yeah, quite possibly. At any rate, it should be doable in the long run