Hi RLT431,
Don't worry, as DaveH pointed out, Mears is a pretty known quantity. You know what you are getting for the $$$, just be prepared to make lots of "mooing" sounds.
For Mears, you will have to buy TWO adult round trip tickets. If they are already included in your package, then you may still want to go with a towncar or limo, but thats going to be money down the drain. I don't know what the Mears policy is regarding children, but you may have to purchase a ticket for the child as well.
When you go by towncar, its not a per person thing, you get the car for the round trip price PLUS tip. Yourride lets you have that helpful grocery store stop. Some people have gone to fast food or the disney discount store. I don't know if I'd do that personally, but hey, whatever floats your boat.
Here are some costs from Yourride's web site for a Towncar Round Trip from Orlando International Airport:
(I'm not sure which resort you are going to so I listed a few of the options here.)
$85 to Magic Kingdom Resorts
$80 to All other Disney Resorts
$70 to Lake Buena Vista
$70 to Universal Studios
Be sure to goto their web site
www.yourride.net and print the discount coupon to get $5 off the cost of your trip. As far as tip goes, I'd recommend tipping on each leg of your trip in case you get a different driver. As many posters have said, $10 is a good tip each way. (1/2 of the total cost=$40, based on $40 a $10 tip would be 25%)
Hope this helps!
Darian