Re: spare time
It is really tough to participate in parish life when you're gone all the time. One thing is make sure your priest knows the situation at your home parish. The parishes you spend half time in, let them know too. Some will pretty much say all you can do is tithe, but I don't think that's the answer. Let them know when you'll be around and what you can offer. You could be on a fill in list, but that's hard when travelling too. I like the website idea, if you are able to design and keep up with that.
It depends a lot on whether you always travel to the same place or not and if you have a. A pretty set schedule. That has been my experience. My schedule was pretty set, though, and always to the same place, so I had an every other week CCD class for awhile.