Some will say no, but I say sure, especially if you're going to halve the time.
This is excess activity that isn't part of your normal daily routine. Your body hasn't become as effecient at that as it might be at, say, just walking. It's much more loggable than "I walked a total of 2 miles around campus between my classes today".
You certainly won't feel like exercise again today anyway!
I would suggest logging it as just one hour of low-impact aerobics. The reason is that when you log more than an hour, because the estimates include the BMR figure, it really starts double-counting. If you log 3.5 hours, you're going to count a lot of calories you really didn't burn. And also, how much time was spent planning, prepping, doing lighter work tasks, resting, eating etc?
So I would, for me, compromise by logging one hour of some form of exercise (and low-impact aerobics is a good catch-all). But not more.