Mariposa is about 1 1/4 hours to the Valley along the Merced River. The road is gently curving & ascending and is scenic for much of the way. You'd enter thru the Arch Rock entrance and Highway 140.
Oakhurst is about 1 1/2 hours to the Valley on a mountain road. Highway 41 is curving, goes up to 5,000' at the South Entrance, down to 4,000' in Wawona, up to 6200' at Chinquapin Station (turn off to Glacier Point), and down to the Valley at 4,000'.
Tioga Pass road & Tuolumne Meadows might not be open by Memorial Day. http://www.nps.gov/yose/planyourvisit/tiogaopen.htm Hopefully the Glacier Point road will be.
Here is a mileage & driving time chart from Yosemite Valley: http://www.nps.gov/yose/planyourvisit/upload/mileages9-2007.pdf
Additional driving estimates (mine, not official!)
Mariposa to Glacier Point: 1 1/2 to 1 3/4 hrs
Oakhurst to GP: 1 1/4 to 1 1/2 hrs
Mariposa to Mariposa Grove of Giant Sequoias: 2 1/4 hr
Oakhurst to Mariposa Grove of Giant Sequoias: 1/2 hr
Mariposa to Tuolumne Meadows: 2 to 2 1/4 hrs
Oakhurst to Tuolumne Meadows: 2 3/4 hrs
I am assuming that you will be driving the speed limit (35 mph most places.)
I don't really have a recommendation for you ~ just information to help you make an informed decision. There are plenty of people who are happy with the lower prices in Mariposa and in Oakhurst, and who don't mind the longer drive to save lodging dollars.
One idea (don't know about finding lodging ~ just an idea)
Day 1 ~ Mariposa Grove in the late afternoon after your long drive, stay in Oakhurst.
Day 2 ~ Glacier Point, then drive to Valley. Stay in Mariposa.
Day 3 ~ back to the Valley or Tuolumne Meadows if open. Stay in Mariposa.
If you're planning to arrive late, I'd suggest staying in Mariposa for the first two nights, then staying in Oakhurst on the last night and going to the Mariposa Grove on your last morning.
Here is the Yosemite Guide page with info: http://www.nps.gov/yose/planyourvisit/guide.htm