We were thinking of making reservations (we love off season here) and recently checked this out on their web site because we are a little unsure of our arrival date. Their campsite reservation policy as shown on their web site HERE
states there is a $50 minimum deposit that must be received within 7 days of making the reservation. Cancellations 7 days or more prior to arrival date are subject to a $10 fee. Cancellations within 7 days of arrival are subject to a $50 fee.
Modifications of the reservation are defined as a change around or within the initial dates reserved
(i. e. changing your arrival and/or departure by a few days) and may be made up to 7 days prior to scheduled arrival, apparently with no penalty. It doesn't say what happens if you want to make a modification within 7 days of arrival. Changing to another week or month which would be outside your original dates is defined as a cancellation and new reservation for a new time period (NOT a modification) and is subject to the cancellation policy ($10 fee 7 days prior to arrival and $50 fee within 7 days).
Maybe the confusion is caused by changing to another week as opposed to changing your arrival by a few days. If you want to make absolutely sure, you could call Ocean Lakes to verify their policy.