We were in Yosemite this summer (August). Rented an RV which slept 7, cost around $1000 + $200 or so for mileage + gas. Sites in the valley are cheap (around $30 per night) but you need to be ready within a few seconds after registration opens around 5 months before.
Brought almost all food with us, you can buy essentials (eggs, milk etc) in the park or in one of the villages on outskirts.
Chabdad in Fresno should have minyan I think - but check with them. They also offer kosher meals service, which we did not use as was fairly expensive. It is closest Chabad to both Yosemite and Sequioa national parks.
Yosemite is wonderful, you'll have a great time.