PS belt = Power Steering pump belt. AC belt = Air Conditioner compressor belt. One of these belts also powers your alternator. You got 90,000 miles out of these belts, now's a good time to replace them.
Fresh coolant (anti-freeze and water mix) is a good idea too. This will prolong your cooling system parts (water pump, radiator, heater core). Fresh anti-freeze helps keep your car's engine cool in addition to protecting it from freezing.
It's probably a convenient time to replace the water pump since there's very little additional labor once it's all taken apart for the timing belt. If it were my car, I'd make the gamble that the water pump won't need replacing until the next timing belt, but others will probably disagree and tell you to replace the water pump while you're changing the timing belt. The choice is yours.