Every one of my Caravans ('03, '05 and three '07s) made that rattle sound. One had 30K, one had 165K.
I replaced the pulley on one of them (my '07) with a solid one and drove it for 35K miles without issues so I did the other four. No problems, no noise, no bull poop. I have a total of 80K miles between five vans with this modification in place and not a single problem.
I did replace the idler, tensioner and serpentine belt on each van when I installed the pulleys.
The pulley I used has this PN:
google it and you will find the source. Cheaper than a new ADP and lasts forever.
You will also need the special tool to get the ADP off, and I recommend soaking the shaft with penetrant. Aero Kroil is my favourite. An impact gun zips them right off. Into the scrap bin they go, the new pulleys come with nuts and a lockwasher.
I removed the EGR valve to get the alternator out, you will need new gaskets. MAKE SURE THE LOWER EGR VALVE BOLT GOES IN STRAIGHT. Very easy to cross thread.
I wanted to wait and get some time/miles on these to verify that they work without issue before posting about it.
The ADP makes sense and I think they're a good idea in theory, just not reliable or cost effective. I've never had a problem with any other rig that had solid pulleys so I figured it was worth a shot. The earlier 3rd gen and later 5th gen rigs have solid pulleys from the factory.