Here are a couple free Kona activities, the first is at The Shops at Mauna Lani on the grounds of the Mauna Lani Resort about 30 miles north of Kona.
I’ve been meaning to go check it out for a while. I didn’t stay for the entire show but from what I saw it was very good.
It’s a pretty high tech hula show with the video playing behind the dancers.
There are 2 shows every Mon. Wed. Thur. Fri. evenings at 7 & 8PM.
But I would call the shopping center first to verify days and times at 808 885-9501. Things change all the time. For example, they have conflicting times from their website compared to the signs at the event.
Update of Free Activities
At the Keauhou Shopping Center 5 miles south of Kailua Village off of Alii Dr. they have the following:
Wednesday
- Ukulele Jam Session 6-8PM
Thursday - Kapuna Crafts 10AM-12PM
Friday - Hula Show 6-7PM
Saturday - Farmers Market 8AM-12PM
Last Saturday of the month they have a free benifit concert in front of Long’s Drugs.
I’ve been to the hula show a couple of times and it’s as good or better than any show you’ll pay money to see in Hawaii.
Another free thing to do.
About 25 minutes north of Kailua Kona off hiway 19 the Queen Ka’ahumanu Hwy, which the locals call the “Queen K” hwy, is another one of my favorite free Kona activities. The Waikoloa Petroglyph FieldWhat’s a Petroglyph you ask? It’s an ancient carving made on the lava flow.
The Hawaiians would use a pointed stone with another rock as the hammer to chisel out their designs. Different symbols represented different events in their lives like births deaths and even surfing as evidenced by this picture. 
The area where the Petroglyphs are located is about a quarter of a mile north of the Waikoloa Kings Shops, located on the Kings walking trail which runs north and south for miles.
You can pick up the trail to the right of the gas station at the Kings Shops. It’s clearly marked with a sign. Make sure to wear sun screen and bring water. There is no shade and it’s usually hot out on the lava.
Another interesting fact about the area where all the Petroglyphs are located is the rocks stacked in half circles built to shield travelers on the trail from winds. This photo shows a lava cutaway that was used for shelter.
This area is very windy most of time. People who live in Kailua call it Waikablowa instead of Waikoloa.
Things to remember on this little outing: Bring water, wear a hat, put on sunscreen, wear good shoes or you’ll be sorry.
Directions from Kailua: Take Hwy 19 north 25 minutes to the first stop light after the airport and turn left go about a quarter mile and then turn right at first parking lot next to gas station, park and then walk to right of station and pickup the Kings trail. Have fun.
As far as free Kona activities goes, this is pretty good.
Here are some more interesting free things to do.
Mauna Kea Summit & Ellison Onizuka Visitor Center Mauna Kea summit is a fascinating place to visit. Your rental car company will not recommend you take your two wheel drive vehicle up there, but in good …
Lava Tubes Lava tubes about 1/2 mile south of Honounou. Take the kings trail and follow it up. I don’t know if they are still accessible or if they have been fenced ..
Get a plate lunch and go to the old "A" and watch the sunset.