Yep, Jim and I were down there in August 2012. We came down the trail from the JMT and didn't cross the river, but we did walk out to the river at Simpson Meadow and ate lunch on the bank.
Simpson Meadow is, as somebody mentioned, not much of a meadow anymore. There are some grassy areas, but it is deep grass in standing water - a beautiful wet meadow, but not a place to camp. Don't be surprised if you don't find anything that looks like a meadow, most of the canyon floor is wooded - beautiful big old growth trees, spectacular place.
The river would have been easy to wade given the water level when we were there, probably knee deep.
When we descended Goddard in September many years ago, we camped on the north side of the river. We had a storm overnight, and awoke to several inches of snow and socked-in wet conditions. We were in no mood to wade so we walked along the river until we found a log. (FWIW, the following two days, hiking up the trail to the JMT and then via the JMT to Muir Pass, was one of the most spectacular two days of scenery we've ever encountered -- ground and trees covered with snow, puffy clouds in and out of the canyon exposing and then hiding the granite walls)
On our Aug 2012 trip we met a trail crew down at Simpson Meadow. They were planning to spend a day or two downstream from Simpson doing basic clearing (cutting logs) on the trail. But they didn't set expectations that they would do enough work to make it really passable, and anybody planning to hike that spectacular piece from Simpson to the dome ought to assume they will frequently lose the trail.
That part of SEKI doesn't get much use, which is too bad. The trail from Cedar Grove to Simpson and up to the JMT is maintained and straight-forward, and it's a shame that thousands of people hike the JMT and few venture off to places like this canyon.
Descending Goddard, on the other hand, is an undertaking for the skilled off-trail hiker, not for the timid. The upper parts above timber line are like other class-2 rocky traverses in the Sierra, but the lowest stretches where the vegetation gets dense is a "really glad I did this but not sure I need to do it again" experience! I'm glad we made the two descents (Goddard Creek and Disappearing Creek through the Enchanted Gorge) when I was young and strong and brave.
Oh, and when we climbed Tehipite many years back there were just 2 or 3 entries per year in the summit register. It's a worthwhile destination, beautiful, and not often visited. We followed the route Secor describes, and excepting a single exposed class three move (for which I was roped) it was not difficult, just a very long way from any road so not frequently visited.
Tom - we hope you have a fantastic trip with good weather. Amy & Jim