For something like a text adventure the language used isnt hugely important, just use what you're confortable with. It sounds as though youre leaning towards some form of AMOS, which will do the job nicely. As for which AMOS, I'd go for AMOS Pro without question. It's the most updated and most system friendly AMOS version around.
Although Amiblitz or C are my favored languages for the amiga these days, there's no denying that AMOS is good fun still, and it is better than it's reputation (which was in part carved by the fact it's so simple to use that people with no real coding skills, but raw enthusiasm managed to satisfy their creative urges (ergo a lot of crappy stuff)). Stuff like Babeanoid shows that quite nice results can be obtained...... sheesh, now Im feeling nostalgic,.. might have to have a play with AMOS Pro again myself I think

At the end of the day though this is the classic amiga we're talking about, a person isnt going to get rich or reach a massive audience with what they create, so as long as you have fun that's all that matters

Feel free to ask for any help when/if you need it.