You might mix it up a little. Jack's and the other Kona boats usually head south. From the Orchid you could also consider Kohala Divers or Blue Wilderness who dive north. The reef is notably different in either direction. BW has a shop close to the Orchid in the Queens Shops at Waikoloa, they use the boat launches at Puako or Kawaihae. Kohala Divers has a shop in Kawaihae and moors their boat there. Both are good outfits and much closer than driving down to Honokohau. I have been out many times with Denise at BW, always happy, have good friends who regularly use Kohala, same story.
I use a 3mm shorty much of the year, local water temps are still up and that is probably enough for most folks, unless you are prone to being cold.
Decent diving right in front of the Orchid, you might throw in a shore dive or two! Try just to the north of the cove. We have been diving from the beach access at Holoholokai, just the other side of the golf course.