Per person you need 3 liters of water to do this trail.
For parking, you can do the parking at the start of the trail. I got lucky twice.
You can also park on Vineyard Avenue, this adds up a little bit more of a hike but beats going to Ohlone.

If you take Peak Meadow trail it is nicer, the trail is less wide and less people. In some spots there is shade. Basically where you see the river in the map is where you have shade and can stop for a little picnic or a break.

I usually do this trail all the way to mission peak.
Then if I am tired of lazy I do the hidden valley back
if I am in no hurry I take the peak meadow route back.
Hidden valley as others mention has no shade but is faster.

There is a stretch at horses heaven trail which is very steep, this is easy going up but is tricky going down. If you are not comfortable with steep downhill. I'd bring a walking stick or poles
and make sure your shoes can catch the track
one time I brought flat-ish shoes and that was a disaster.

Mahalo