Insurance costs can vary by State, County and HOA.
We have 2 playgrounds, sidewalks a bus stop shelter and carry a 1 million dollar liability policy.
Regarding reserves, what you will need to put away for expected maintenance of trail, playground, and pavilion will vary. If you haven't had a reserve study done in the past, you should have one done.
If the trail is dirt, you may need to grade and regravel.
If the trail is asphalt, you will need to seal, and repave.
The pavilion (like our bus stop shelter) may need to be powerwashed and sealed every few years.
At some point in time it will also need to be replaced.
Regarding playground equipment, it will need replaced over time. There will likely be unexpected repairs as well. mulch/padding will need to be replaced and topped off over the years.
To learn more about reserve studies, see the following thread in this forum (it's a link to the thread):
Subject: Reserve Studies/Funds 101 To determine insurance costs, write a request for proposal identifying the common elements the Association owns and contact insurance agents. I would suggest a million dollar liability policy but let the agent know that you are open to hearing options they would recommend.
Hope this helps,
Tim