That's thinking too much. Why not just bomb every planet and save on a ground war. Where is the fun in that. The usually way around this plot point was to say the planet has shields so you have to conduct a ground campaign, like on Hoth. Also, the attack on Geonosis was not just to save three people. The Republic found out the Separatists were building a large army there and were planning to attack them. As for the Jedi. What sacrifices are you talking about? How are the Jedi making things harder than necessary?