How much time for February safari and beach adventure

My wife and I (mid 60s) are in the midst of planning a bucket list Tanzanian safari and Indian Ocean beach adventure for February 2026. We selected this time because, from what I understand, it coincides with one of Tanzania's "dry" seasons. might have slightly fewer visitors than the June-Oct. high season, would encompass the calving season with the opportunity to see lots of babies and predator activity. I believe the best places to safari this time of year would be Ndutu, Ngorongoro, southern Serengeti, and Tarangire (maybe not for the calving, but for elephants, etc.) I have a couple of questions as we start to make inquiries with some safari operators we have identified: 1. How many days would be adequate to get a full safari experience in the areas I mentioned above? I realize this can be subjective, based on one's interest, etc. --but I guess I am looking for a general rule of thumb. Would a week be enough time, 8-9 days? We love wildlife and if our experience is anything like some of the YouTube videos I've seen, I'm sure we'll be blown away, but at the same time, how many days of hours upon hours on the road would start to get to be overkill (and overly expensive)? While I know movement from one lodge/camp to another is going to be necessary to position ourselves for a fruitful game drive in each area, it would be nice to be able to stay at a lodge at least 2 days in a row, rather than move every day---not sure if this is possible for a week's time frame. 2. If you were to visit in February, in what area would you spend the most time? 3. We do plan to spend an additional week on the beach. I know Zanzibar is world renown for its beaches but from what I've come to learn, the beaches in certain areas are subject to extreme tides that make swimming almost impossible at certain times of day. In addition, I've read that the constant harassment by beach vendors can get kind of annoying and renting a car can be risky, mainly because there might be a good chance of being shaken down by corrupt police. Are these concerns overblown? Is another island like Pemba a better alternative? Thanks for any guidance you can provide!