You won’t need four-wheel drive to go to Carara National Park (Carara is right off the main highway) or for Manuel Antonio or Rainmaker. The road to Rainmaker is bumpy dirt but it’s nice and flat. A higher clearance 4WD is nice to have though in Uvita as many hotels, restaurants, and attractions are located in the mountains up steep dirt roads (some 4WD required). It really depends on the specifics of where you’re going in Uvita and what you’re doing there though.   
 
For drive times, Google Maps is pretty accurate for getting from Manuel Antonio to Uvita (about 1 hr) and Carara (about 1.5 hrs) as it’s all smooth paved highway. For Rainmaker, it’s about 45 min. We have detailed directions in our post on Rainmaker: https://www.twoweeksincostarica.com/rainmaker-conservation-project/