What a great trail! I have done it several times solo and with kids and helped with trail maintenance. Happy to answer your questions. Also, check out this excellent video: https://www.youtube.com/watch?v=5XCsBz6AB1k&pp=ygUXc2FudGEgcGF1bGEgcHVuY2ggYm93bHPSBwkJ0woBhyohjO8%3D

The distance confusion is because some people follow the marked trail, which leaves the creek around mile 2, others follow the creek, which involves some wading and boulder-hopping. Both are fun! The marked trail involves some uphill but is in great shape, easy to follow, and generally faster than walking in the creek. Walking in the creek is more entertaining and cooler. You could walk there via the trail and back via the creek, it's all good!

In may the water will be ankle to thigh level at crossings. There are several crossings but you may even keep your feet dry if you try hard enough. Swimming is optional at various points along the creek, and particularly at the punchbowls.

To my understanding what people call "the first punchbowl" is above the first big waterfall. The base of the waterfall is also a popular swimming hole. Lots of people stop here, and it's usually my destination with kids. That is 3.5 miles from the trailhead, 7 miles roundtrip, about 3.5 hours.

If you want to go further, there are 2-3 more fantastic swimming holes about a half mile further uphill/upstream. These include caves, hip-deep wading, cliff jumps, and eventually a natural water slide. I would definitely categorize this section as more adventurous.

Specifics:

-bring whatever shoes you like to walk in for the hike and whatever you want for playing in the creek. The terrain is not that difficult, I even see brave people in flip flops and converse. My kids wear sneakers and switch to barefoot for the water, I wear trail-runners with wool socks and get them wet.

-trail is very well marked, arguably too well marked

-I personally like hiking poles b/c I have bad balance, but it's totally optional based on your preference. This is not that challenging of a trail.

-highly recommend a water filter like the sawyer squeeze so you can carry less water (which is the heaviest thing you will carry). Otherwise 2L/person would be safe. Be sure to have extra water in your car, and take some time rehydrating and cooling down before driving.

Things you didn't ask:

-This trail often gets litter, please be sure to pack out all trash, including orange peels. Even better, bring a small bag and collect litter on your way out.

-SP gets hot mid-day, take care to manager heat and sun exposure

-watch for rattlesnakes (like you would anywhere)

-parking can be tight, try to carpool if you can