Hi Kitty,
Yes, Yes, Yes, imho, having a car allows YOU to be in control of your vacation.
I have always rented a car because we like to go to other places besides disney. Like you, wer usually split off/site on/site. We like to go to Universal, too.
You are also going to be Orlando for a long time. Having a car gives you freedom to eat off site, drive to other parks without worrying about shuttles or other transportaion, gives you peace of mind should someone get sick You need a drugstore). allows you to buy a few groceries during your stay. A car allows you flexibility should you decide to check out say the town of Delebration or other parts of Orlando.
I have never regretted having a car. Yes, prices have gone up this year, but check out mousesavers.com for codes. and check out Dollar and National at the airport onsite for best service. L and M is probably going to be cheapest onsite at the apirt., but there is mixed reviews about this service.
PM me if you have more questions. There are also coupons in the ent. book. Herc.