Personally, I prefer taking a taxi to and from the airport and Universal (or other Orlando attractions). I had several bad experiences with Mears, mostly ridiculously long waits for other people so they could have a full van. Then they often stop at numerous locations along the way.
I thought I was all set and scheduled a pick-up at CBR to go to IOA. I ended up sitting in the van for 45 minutes until another family finished their breakfast, then we had to stop and pick more people up at another WDW resort, then stop at Sea World, Wet N' Wild. Needless to stay I finally arrived about 90 minutes behind schedule. I also took a very early flight once so I could get to the parks right when they open, only to sit at the airport and wait for people whose flight was delayed for an hour.
The cab fare from the airport for a family of 4 are cheaper than you'd pay for Mears anyway, and alot of the cab companies will send towncars or vans for larger familes. I'd look into the car rental if you plan on going to BG-Tampa.