another silly beginner Q - re: rest days

My thought: don't let triathlon get in the way of the rest of your life.  If you enjoy swing dancing then have at it, and if you're a little sore/tired the next day then modify your Sunday workout. 

One suggestion: I'm not sure what your general schedule is like but most people would plan a week day for their rest day, if they have one.  You might find a better training structure if you plan something for Saturday's/Sunday's--generally the longer sessions--and take Monday off, or do some yoga/stretching for help with flexibility and some active recovery. 

As far as general 'what to do/what not to do' on rest days and in general: only you know the answer to that.  You're just getting back into training so give yourself ample time to recover and let the body readjust to the training.  If after tearing up the dance floor you're feeling less than perfect on Sunday then use that as your rest day knowing that you had fun and also got a good workout in on Saturday.

Hope this helps!

I agree.  Live your life, and work triathlon in around it.

I would say that you should consider swing dancing cross training and take a different day as a rest day.

In general, a short walk around the neighborhood is about all I would recommend for a rest day... nothing that will tax your body. Remember, the purpose of a rest day is to all your body to take advantage of all the time you have put in to build it... it's on rest days we get stronger!