Thanks everyone for all of the good info!
Is the etiquette to tip the rangers, or will they refuse?
Do the rangers lead walking tours, or do they get into the car with your party and drive around with you? Or both?
Battlefield Guides and Park Rangers are two different things. Park Rangers work for the National Park Service and, as part of their job, provide ranger-led events/activities as a part of the park's official offerings. They do not drive guests' cars.
Antietam Battlefield Guides are a group of historians dedicated to providing outstanding interpretive tours of the Antietam Battlefield, as well as other sites related to the Maryland Campaign of 1862. These guys enjoy taking people (groups or individuals) out to see the battlefield and other historic places and they usually will drive your vehicle. Different ones are available different days and can be arranged through the Antietam National Battlefield Museum Store. They have a menu of "standard" tours they will do for those who do not express specific interests. Here are descriptions and rates for 2, 3, 4, 6, and 8 hour standard tours.
https://antietamguides.com/tour-rates-2/
If you have a specific interest (ancestor's regiment, certain brigade or part of the battle, etc) most are able and happy to provide a more specific tour. Or if you want a tour with more walking or incorporating a hike of a specific part of the battlefield. For either, I would
definitely suggest that you make arrangements in advance.
We booked a specialized all day tour with
Stephen Recker and he was fabulous! He geared our tour to the brigade my husband's ancestor was in and provided info down to the regimental level (16th GA/Cobbs). He is not researching Cobb's/Wofford's brigade, per se, but he took the time beforehand to do a ton of research
just for our tour in order to provide accounts, specific information, and match the tour to specific places. One of his research interests is historic photographs of the area, so he brought along lots of old photos to show us what places looked like before, during, or soon after the battle. You'll need to make arrangements in advance, but if you are lucky enough to get Stephen, you will not be disappointed! Ill PM you his email address.
If you'd like to select a guide based on area of expertise, you can look at their bios here
https://antietamguides.com/antietam-guides/ When you make your advance reservation call the Antietam National Battlefield Museum Store at 1-866-461-5180 or 301-432-4329 and request a specific guide.
Regarding the etiquette of tipping, I think it is always nice to offer a tip in recognition of outstanding service. I don't think Park Rangers are allowed to accept tips during work hours, but Battlefield Guides dont work for the park service and tips we have offered to Battlefield Guides have never been refused. I hope you enjoy your visit to Antietam!