I've stayed at the Hilton in the Taksim district several times. It is quiet (unlike many hotels in the older districts) and has a nice view of the Bosphorus. Plus, there's always that HHonors credit to consider. There is also a very good buffet breakfast included. To get to the older parts of the city you will need a taxi but they are plentiful and cheap. Istanbul has to be one of my favorite cities, and it's hard to imagine anyone having a bad time there. The grand bazaar goes on forever, but most of the merchandise is repeated over and over. There seems to be a system where each of the stalls is obligated to buy from the same wholesaler. The Egyptian (spice) bazaar is more accessible, and there is the added advantage that just outside the bazaar is a shopping area(meaning the stores on the streets adjacent) frequented by Turkish residents, without the cheap trinkets.

I also recommend without hesitation the ferry boat that takes you to Buyukada for day trips. This island has no cars, and instead you hire a horse buggy and driver to take you around.

The Bosphorus can be seen from Tourist excursion boats, or from the state ferry at one tenth the price. I've done both, and the only real difference is that the tourist boat has a canned monologue on a speaker system.

Hope you have a great time! Woody