There are two airports in Houston. If you fly into IAH (Bush) a Continental Airlines hub, you're 70+ miles as previously stated. If you fly into HOU (Hobby) a Southwest Airlines hub, you're a little over 50 mile from the pier. The cruiseline offeres transfers from IAH only. There is an outside transfer company www.galvestonlimousineservice.com
1(800)640-4826 that will provide transfers from either airport. There may be add'l options for rental carss/vans/limos but I don't know the cost.
There are plenty of hotels in Galveston on or near the beach. The nicest of these is The San Luis Resort on Seawall Blvd. The pier is not near the beach/tourist areas, it's in an industrial district. That means more transportation needed if you stay at the beach. The beaches in Galveston are not much to brag about unless you like brown water. There is plenty to do in the area. NASA, Kemah Boardwalk, The Strand and more in Houston. If you're going to spend time, the rental car/van sounds like a wise investment.