I am a black belt in hapkido, but my instructor also teaches me and a few other students in yang style tai chi. (Don’t worry about the different styles, I’m just sharing my experience.) I find tai chi very interesting, mostly because I routinely practice what would generally be called a “hard” martial art (though it is a balance between soft and hard styles). Tai chi is generally considered an internal art, making it much different and an interesting physical and mental challenge.
It is not aerobically strenuous, but it is more demanding than simply gently waving one’s hands around in the air. To do tai chi well, you need good flexibility and strength, especially in your legs. But this is something that is developed over time, and lack of those attributes isn’t an instant disqualifier as it may be in other martial arts. You aren’t going to get fit and lose weight doing tai chi, but after an hours’ worth of practice, you do feel it some! And don’t be fooled: just because you see real old people doing it, doesn’t mean that they’re your typical frail old folks: quite a number of elderly practitioners are surprisingly strong and flexible for their age, probably because they’ve been doing it all their lives. Check out Youtube and you’ll see what I mean.
I’d still consider myself in the intermediate range of skill, so I’m no expert, but here’s my thoughts on who may get the most out of tai chi:
You should have great patience and be inclined towards perfecting a fewer number of things, rather than seeking to learn a greater number of things with somewhat lesser precision. Odds are that in six weeks you’d be learning only one form the whole time, so if you need excitement, changes of pace, or to mix things up to keep your interest (rather than doing the same thing over and over to perfection), tai chi might not be as rewarding.
You should commit to taking it seriously, devoting a lot of thought and brainpower to the movements, but clearing your mind in an almost meditative sort of way. The kicking I do in hapkido is rewarding because its all about speed, fast-twitch strength, and turning your brain off and letting your instincts take over. One might compare that to watching an action movie; in which case tai chi is more like reading James Joyce, because the rewards are not instant gratification, but the result of considerable and sustained effort.
Although tai chi does have some self defense applications, I’ve found that the lessons are very subtle and it takes a very, very long time to “get” the hidden applications, and probably only valuable to those who have already spent many years studying martial arts and who are seeking advanced refinements of techniques and concepts already introduced elsewhere.
So that is kind of what it is like in one person’s eyes, but someone is very well advised to take the same steps as any martial artist would give to any beginner. Meet with the instructor first, get a sense of whether the guy is actually an expert in tai chi or just picked up a few things watching a video and reading a book or two, ask to watch a class and think how you’d like to be taught by that instructor (I did a bit of tai chi when I was in China years ago, and the instructor was incredibly demanding – stretch more! reach further! deeper stance! bend down further! – which some may not expect out of a tai chi instructor), and if at all possible do a trial class.
It sounds like this may be more of a community college/rec center type of deal, so that advice may not be realistic. But $99 seems a reasonable price to me, and since it is a pretty short term commitment, I’d have less hesitancy so say why not give it a shot and see if the husband likes it, and if not, hey, it is only a hundred bucks.