I've lived in Austin 15 years and this was my first time here. The creek was flowing and the weather was a perfect 73 degrees and sunny. (Although we're expecting SNOW tomorrow!) I took my 5 year old daughter and one of our dogs with me. The hike was moderate for the 5 year old, but the water crossings kept her very entertained. She did slip and get dunked once, but she thought that was fun! Wear Tevas or some other water shoe. This hike is not stroller friendly so don't try it. There are 13 water crossings total. Be careful before and after crossings as the mud is very slippery.
There were TONS of dogs, most off leash. The majority of them were friendly. We had three instances that could have turned ugly. My dog was on leash and I would suggest you do the same unless your dog is 100% on recalls and non-dog agressive to the extreme. We had two dogs gang up and start posturing. It would have turned into a fight if mine wasn't well socialized/trained. Another took a cheap shot and BIT my dog without warning. Just a snap and release as he was walking by. A third mounted my dog. All three cases were off leash dogs well ahead or behind their owners. Unless your pets are very well socialized and trained, I suggest leaving them at home. If they do listen and play well with others it's a BLAST for your four legged friends. Just keep an eye out for morons. And please pick up poop and PACK IT OUT! Leaving bags trailside is just gross.