The baby care centres have nursing rooms (with plugs, rocking chairs, dim lighting, etc...) which I used frequently during a trip we took when my daughter was four months old. There was usually at least one mother pumping in the nursing room (sometimes several) so you shouldn't have any issues. In some parks the nursing rooms are private, and others its a room with about a half dozen rocking chairs. There is only one baby centre per park (as far as I know), so depending on where you were in the park, it might be a bit of a hike. Not sure how often you pump, but if its every 3 or 4 hours, it could be a good break anyway.