As you are coming from Iowa, Hawaii will be about 5 hours behind you. I suggest you take advantage of the intial jet lag by doing the Haleakala sunrise earlier in the week. The recommendation is you leave your hotel about 3 am. For you, that will feel like 8 am, so it is not so drastic.

However, that also means for the first few days, you will want dinner about 2pm and be asleep by 8!
I take advantage of this to have lunch at a nice restaurant and skip dinner, having only a glass of wine and some snacks for "dinner" at sunset, until my clock is reset.

Make that Hali'imaile General Store. Sashimi Napolean is a must.

There should be some lavender in bloom as the farm has many different varieties growing. Besides viewing lavender, you can get lavender tea and scones, or lunch made with culinary lavender, as you enjoy the scenery. (resv req)The views are breathtaking. They have scheduled tea time/farm tour at 10 in the morning but you can also get tea and scones anytime outside the gift shop. You are also free to walk the property on your own. The terrain is sloped so have good walking shoes. I love their gift shop! They have cute lavender bracelets with dragonfly charms--their logo(dragonfly).

Upcountry Maui is so different. Yes, the beaches are spectacular and wonderful and everything you could wish for, but upcountry has a cooler climate, and is more mellow. I would love to have a house up there with those views. Me and Oprah, I guess.

Back to the Table/Ground:

Chairs with backs? Opt for tables.
Chairs w/o backs? Ground is authentic.

Having been to Old Lahaina Luau- I would take the tables. It's a fairly long program and it is not that comfortable on the ground. It is much easier to get up and walk around to get another view, or another drink, when you are at a table.