Need a week 5-7 days, so it's not a big rush...
There's several types of bus tours there
maybe need to call, I don't remember specifics
what I remember is;
contact a local tourism company,
in whatever town or lodge you plan to stay at,
unless you want to camp, or a motorhome with hookups,
& it ain't cheap
(
need wildlife/bear esp. proof containers when you leave the campsite
put your food ****/maybe even some personal belongings, on a rope up in a tree)
& you better make reservations, now or some are
almost a year in advance for the lodge or better campsites, with any amenities...
I don't know any 'off hand' right now, been way too long now
*some private tours too, contractors in the area,
depends on where you stay which are closest & have a shuttle to the park
or pick you up at the lodge or your hotel
lots & lots of options & prices all over the map
*a mini bus, sort of more private for you & the wife, maybe 2 other couples
*van tours, lower loop
*specialized, wildlife focus tours, go deeper into the park
not as crazy with people
*depends on what time of the year traffic in the park can be crazy
wildlife crossing roads etc. & mamma bears Brown or Black w/cub/s,
bison/buffalo or moose with calf/s (they are dangerous), occasional wolf
all of which can be dangerous
Tourists, flatlanders & inner-shitty-dwellers,
all of which are clueless of outdoors, or wildlife
most the people are idiots, with lil' to no common sense
It's almost more fun to watch people
who make really bad decisions then the actual wildlife,
that will threaten or charge them
bring binoculars & good cameras with zoom
you will see a crapload of wildlife, in your own car or in a bus/van tour
Be patient, don't be in a hurry, it won't do you any good
(
too bad you 'don't drink', maybe you'll start 
)
lots of jerks & traffic, people doing really stupid **** & walking along the roads
in peak season, flatlander/shitty dwellers, trying to get too close to wildlife
some of the more popular stuff/sights, isn't really very good
over hyped & way too many people
go to them later in the day if you can, not so many idiots & their kids
to deal with
happens every time
been years since I've been there now
Yosemite is a lot like the same deal, depends on what time of the season
Good luck & Enjoy
private or arraanged tours make reservations way ahead of time
& both parks over book like the airlines do, beware