As an alternative, how about using a 12-36 cassette, either with the current 26 tooth front chainring, or switching to a 24.

Another alternative -- put on a standard 22-32-44 front crankset to replace the 26-36-46 -- should be less than $100, and that would make a big difference in your low and you could keep your current cassette. And you'd have plenty of high end if you wanted that.

I too have heard people tell me "you're just going at walking speed in "X" low gear". I've had people tell me that anything less than a 1:1 ratio is pointless (e.g. 27 gear inches). OK, maybe it is for them, but I like low gearing, especially with a load. And if we're talking "walking speed", it's a lot more efficient to spin fast and pedal a bike up a hill than walk it, even if your low is 21 gear inches. And as you say, speed isn't the issue anyway.

In my opinion most bikes are geared far higher than they should be for the average rider.