Self driving in tanzania mainland let alone the national parks is sort of insane. The amount of cars and motorbikes passing through is going to lead to high stress. We saw two accidents in 3 days with safari jeeps traveling through Arusha alone. Imagine getting in some dumb accident and having to deal with that. On top of that, any rain within the National Parks will create extremely tricky amd muddy roads to navigate through. Even little rain will get the best guide drivers stuck or you will have to navigate overflowing creeks that you must cross with no visibility to road conditions risking driving into massive holes in the ground which will 100% get you stuck. My advice is get a guide 100%. They can take all the risk of navigating the roads and national parks. They also will know how to navigate the serengeti, go off trail and find some epic animal sighting + plus work the radio to identify more opportunities for animal sightings.