I don't see anything you're missing except a trashgaurd for your ventpipe. If that gets clogged with some debris and your system starts siphoning, it may not allow enough air to cut the siphon action when the water level comes back down. Then you'll lose all your water down to the intake level.
I did not do an anti-seep colar for the reason you stated, but we backfilled the trench with good clay and compactted the crap out of it with one of those jumping-jack plate compactors. But that was my choice, there are plenty that would recommend anti-seep collars for insurance.
Post some pictures when you install the pipe, I'd love to check it out!
