Just a suggestion from personal experience on my visit in January:
Take the First Ferry to Lantau (you get it just about 100 meters from Star Ferry Central terminal). Then take the #2 bus to the Po Lin monastery. It's a pleasant ride (30 or so minutes?) that'll give you a feel for some parts of Lantau that you otherwise wouldn't see. Take the cable car (Ngong Ping) DOWN the mountain to the MTR station for your return. It amounts to a very pleasant half-day outing.
There was an amazingly long line waiting to go UP the mountain (I estimate at least an hour wait, maybe longer), but no wait going down.
Sorry, I don't remember what day of the week we went.

Thanks for all the suggestions. I've got lots of time to think things over. Ray, you're right. I've got to loosen-up our schedule a bit. I was a bit rushed when I picked the schedule for our trip so we can't avoid doing either Ocean Park or the cable card on a weekend and on the last day. I wish we had more time.