So is the ZR850... but the Elura100... if you can find it, get it... of the 3, it is the only one with a mic-in jack. Of course there is the ZR800. Be warned: NONE has manual audio control, so overdriving the auto-audio level circuits with loud music will render the audio useless. 10x is plenty - depending on how big the park is Video is more than the image - a lot comes with the audio, too.
Just because a camcorder has 3CCDs does not necessarily make better quality video - is that single CCD or CMOS is big, the video could be quite good.
Of course, all this presumes you have a Firewire port on your computer - and you intend to buy a Firewire cable when you get the camcorder because the manufacturers do not include that particular cable in the box. Transferring video from miniDVtape is done via Firewire (also known as IEEE1394 and i.Link... the cable connects to the "DV" port on the camcorder. USB is used ONLY for stills transfer off the memory card.
The Panny PV-GS320 technical spec (at panasonic.com) indicates 37mm filters - so if you think a lens can use that and you can find a lens to fit that, check it out.