I have wanted to view the Sequoia and Redwood trees for years but each time I start to plan the trip I become overwhelmed and give up and go somewhere else!

We will have about a week for the trip, probably early September. We are not hikers or campers but will enjoy scenic drives, picnics etc.

Have I figured out correctly that the best place to see the Sequioa's is Sequoia and Kings Canyon National park, with Fresno the closest airport? And to save driving time I should stay at one of the park lodges?
I was hoping to also see the Redwood trees on the same trip. Is this reasonable if I have a week? If so, at what location? Should I consider flying into Fresno, see the Sequioa then travel to a new location for the Redwood's and fly home from a different airport?

Thanks for any direction.

"Have I figured out correctly that the best place to see the Sequioa's is Sequoia and Kings Canyon National park, with Fresno the closest airport?"

If you want to see coastal redwoods too I'd forget about SNP/Kings Canyon. You can do a loop out if SFO (or San Jose or Oakland or Sacramento) and visit Calaveras Big Trees State park a little north of Yosemite in the gold Rush foothills and there are two really terrific Redwoods state parks in/near the Santa Cruz mountains south of SFO.

Calaveras Big Trees SP
Columbia SHP
Henry Cowell Redwoods SP
Big Basin Redwoods SP

A week would be easy in/out of SFO (or the other airports I listed) for coastal redwoods, Sequoias at Calaveras, Colombia state park, and maybe even squeeze in a day in Yosemite.

Completely agree with Janis' suggestion. You could include a day in Yosemite, OR (my preference) spend a couple of days around the southern part of Monterey Bay, including some of the Big Sur coastline and incredible Point Lobos, as well as the twee shops and lovely old Spanish mission in Carmel, the terrific Monterey aquarium, and maybe even a day at the old-fashioned beachfront amusement park in Santa Cruz. Imaginary map - https://goo.gl/maps/4seh9NR4bLP2 (Google the places shown.)

Three days in the gold rush country and three in the Monterey Bay area, and you'll be planning your next visit before your first stop for gas.

Well, nothing is "equal" to the General Grant tree (Kings Canyon NP) or the General Sherman tree (Sequoia NP) but the trees in Calaveras Big Trees SP are no slouches. The obvious trade-off is that the Calaveras trees are way more conveniently located than the Sequoia/Kings Canyon parks if you want to include some coast redwoods in the mix in a limited amount of time, and sometimes travel is about trade-offs, innit? And while predictions are dicey, the chances of having smaller crowds and a much easier time of things logistically (accommodations etc.) are way in favor of the northern option; the gold rush country is full of terrific lodging options, and full of delights of its own. For example, Murphys, the town down the road from the Calaveras trees, is a picturesque and historic town, now very much a center for wineries (as is the whole region.) And the string of towns along CA Hwy 49 and some of its side roads are nothing short of fabulous.

St. George Hotel, Volcano CA

I stayed at the St. George hotel, many years ago. Dinner was included with the stay (it was the best prime rib I think I have ever eaten). The saloon, which was part of the hotel, served a drink called "Moose Milk." Fond memory.