Tapering on multiple events

This will largely depend on how well you recover after a race. An
Olympic distance triathlon in not insignificant, especially if you have
done only shorter distances. Your age and overall condition will
determine how well you recover. I'm 40 years young and always take at
least 4 days of complete rest after a race of such distance and then
slowly start training again at low intensity. Swimming is better to
start with since it has less impac, followed by biking and then
running. If you can have a good massage or a few ice baths as soon as
possible after the race will also aid in your recovery. The good thing
is that since you have probably trained very hard for your triathlon
you should be able to maintain your overall fitness for those 3 weeks.
My opinion that less would be more to get from one race to the next
with such a short interval. I always find that I think I feel good
afew days after a reace but as soon as I start running again I still
feel fatigue in my legs. And it's probably more important to get red of
the remaining fatigue then to get more mileage before your second race.