The ONLY way to absolutely prevent the painter getting wrapped on your prop is to bring the dinghy alongside or behind the boat with just enough line between the tow ring on the dinghy and the cleat on the towing vessel that the boat is still floating in the water. This is made much easier by the inflatable ribs that are standard these days. Remember when standard dinghies were fiberglass with rub rails?

Bottom line, always pull the tender up as tight as possible when anchoring, mooring or docking.

As for the OP's question about a towing rig, I think you're over thinking things. From the sound of your trip itinerary, you should be fine just tying off the end of the tender painter to the stern cleat on the cat. Attach the painter to the bow towing ring on the tender at the other end. If you can, it is usually best to tow from the lee side hull. Aside from that, you should be fine. Why worry about a bridle or anything else like that when you're only island hopping sailing an hour or two at a time? Relax mon!

Enjoy!!!