I would not worry about how to translate ご案内しております on its own, so much as I would look at the entire sentence in context and then come up with a natural English equivalent. In this case: "Between April and October, we offer on a first-come, first-serve basis parking spaces for standard-sized vehicles at a rate of 600 yen per vehicle."

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Note added at 18 hrs (2016-11-05 00:34:08 GMT)
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Obviously, you have the full context in the document at hand, so if it is apparent from that context that the hotel has, say, a deal with a neighborhood parking garage that it doesn't itself operate (and hence is not necessarily in a position to "offer"), adjust the language appropriately, i.e, "we can direct you on a first-come, first-serve basis to . . ."