On Kauai, your peak choice, realistically, is down to one, Andrew. KU-011 is easy and everything else on that island begs for a professional guide and a whole lot of trouble. Go to the town of Wailua and travel near the end of Halelilo Road, where you see a sweeping left curve. In the middle of the curve, there is a parking area and trailhead on the right side of the road. Climb 1,000 vertical feet in 1.7 miles. The peak is known locally as the Sleeping Giant. Great view, and not too muddy after the very frequent rains, unlike all the other Sota peaks there. To line up four contacts on 146.52, go to the Kauai ARC on their repeater, 146.920 minus 600, no PL tone needed (last I knew), and do that well in advance of your climb day. Active local hams are Randy at WH7ZI@me.com, Ted at NH7YS@arrl.net, and AH6TA at email@example.com. They monitor the repeater.
On Oahu, there are four easy Sota peaks in a row on the southeast of the island. However, only one, Diamond Head, is in easy line of sight with Honolulu, where many VHFers are located. This peak is in a State park, on the rim of a crater. The park is open 6 am to 4:30 pm going in by car, with a 6 pm deadline to leave by car. There is a small entry fee, even if you walk in. The car and pedestrian entrance is close to the corner of 18th Avenue and Diamond Head Road. There is no other way to get in…If you do HF on Diamond Head, a very crowded place, you have to duck under the rail at the top and go to the right over to the cement bunker. Ignore the signs - everyone else does. There is an iron strap sticking out of the bunker, which I bungeed to my pole and operated in the shade (44 foot doublet) on the edge of an east facing downslope. I saw no park rangers on trail or on peak, but one went up for a medical emergency while K1JD was on top. They told him where to set up but discouraged going to the more ideal bunker… For VHF only operations, it’s OK to blend in with the big crowd inside the rails. I used 146.52 FM simplex on a weekend, after announcing my intention on the local repeater on 146.880 minus 600 (no PL tone needed). The repeater antenna is also on the rim of Diamond Head crater. That frequency is used by a busy net at 7:30 pm, 5 nights a week. I checked in with them the night before activating, stated my intentions, and I got lots of takers whose calls I recognized from the net…47 minutes going up and 18 minutes to descend…Plenty hot, with no water or facilities on trail or on peak
Virtually all activations in KH6 are by visitors like you, which I predicted when that association went live.
Have fun in paradise.