Awesome project!!! Fun to see your helper up there too!!!!
How long are those posts? At 16 feet above grade, they must have been pretty heavy. I've done 16 footers by myself, walking them into the hole and lifting a little as the end slides in and that's about the max of what I can do by myself. I wouldn't dream of trying to get longer ones into the ground on my own.
This looks awesome! The craftsmanship is top notch. Few people that can work that nicely with wood can also do that nice of steel work
I would make one change though - I wouldn't use eyebolts for the tree. There is going to be a TON of pull-out force on those cables if there are a few adults, someone jumps, etc... and being holes in a tree there is the possibility for rot and wood imperfections to cause major issues over time, even with the fact they're quite large. And it would be difficult to detect.
If possible, I would drill straight through and use 3/4 or larger high strength hot dipped all thread to make the connection.
Good looking play place for sure, and I'm thinking hunting might also be in mind there.
For the other end of the bridge you might google "TAB treehouse attachment bolts" there are a couple of engineers who have gotten together and exchanged notes on bolt designs that worked well and did not work well. Accounting for how the tree is going to grow and so on. Pricey for sure but you are planning a very long bridge and might consider their advice. Start here: Treehouse Attachment Bolts (TABs) | Attached Limb Systems
Again, kudos on your good work.
Can you share your rough budget? I too want to temper the families expectations.