Google Maps says the drive time from the rental car center at TPA to Disney Springs is about 1.5 hours -- and that also matches my experience having driven it both directions several times. Of course, that drive time could be longer depending on day of week, time of day, and traffic.
It's an easy drive, expressway almost all the way.
Your group presents several problems. You've got 4 adults and 2 kids with booster seats -- which I assume you are bringing with you. That's a large party, and with luggage you probably are going to be crowded, even if you rent a minivan or large SUV. Of course, if you wedge everything and everybody in, it's only a short drive.
According to RideGuru, the Uber/Lyft fare for XL (which you would need) would be about $125. You could expect some difficulty getting a ride and would probably have to give the driver a big tip up front for the inconvenience of having to drive back to Tampa empty.. For that reason, I think the one-way rental might be a better option. Also, if you don't bring your own boosters, neither Uber nor Lyft will be an option.
I would also research flying into TPA and returning home from MCO. If you fly both ways via TPA, remember to also include the return trip rental in your calculations.