Depending on where you buy your tub you will potentially have the choice to go with a free "spa frog" kit when you buy it. This is a bromine floater setup. I've got a neighbor that uses the spa frog in his Bullfrog and he shocks once a week, changes his spa frog cartridges once a month +/- and does very little else. If he has 4 adults in for an evening he'll throw a little dichlor in afterwards but that's about it.
I think you'd be perfectly fine using a bromine floater with your schedule...