Here’s my recommendation, as soon as you reach the island, take a Tuk-tuk to the viewpoint for ~20 Qz, that is, mirador and when returning ask the Tuk-tuk to drop you in the center of the town. On this island, I took a guide who charged me 40 Qz and gave me a 30-40 minute average tour of the island including taking me to the local Pueblo’s house. I also booked a day tour of Tikal for the next day for 170 Qz.