Tikiland Day is very well attended. The IG page with information and photos from last year is @tikilandday. It is a very fun day with lots of activities. I don't think it impacts ride wait times unless you are looking to ride during one of the take overs.
This is what the schedule looked like last year. When I see the schedule for this weekend, I'll post it.
9-9:30 am - Art drop clues - This doesn't impact attractions or wait times
10 am - Group photo in front of Tropical Hideaway. This will make Adventureland very crowded. If you are going to Indy, it is best to walk through Frontierland and turn left after River Belle.
10:30-11:30 - Treasure Hunt - This is a scavenger hunt throughout the park. It does not involve going on attractions. If you happen to be near one of the clues, you'll see a bunch of people wearing Hawaiian clothing counting objects, entering it into their phone, then darting off to the next clue.
11:30 - 1 pm Lunch
1:15 pm Group photo at the train station stairs This year, the Celebrate Happy cavalcade starts at Small World at 1:30 and ends on Main Street around 1:50. I'm guessing they will adjust the timing of this earlier or later.
1:30 pm Jungle Cruise
After Jungle Cruise - Tropical Hideaway Takeover
3 pm Enchanted Tiki Room Sing-A-Long
Edit to add that it is free to participate in Tikiland Day activities. You might sign up to receive texts and decide if there is anything that looks fun to your group.