How far from the speaker really depends on how far can you see. If you're in thick cover and can't see more than 50 yards, then you certainly don't want the speaker 50 yards away. BUT if you can see a long ways, then you can put it out away from you more.
How much calling pressure have the coyotes had this winter. If you, your cousin, or anyone else has been in the area more than once already and used cottontail distress, then by all means, use a different sound. Howling this time of year should be productive, but again, have the coyotes already heard every howling sound from your ecaller already this winter, if not, by all means, do some female invite., or other non-aggressive howls to start the stand, wait at least five minutes before doing any distress if nothing show up. IF the coyotes have been called to with distress this winter, it could be productive to use ONLY howls, for the whole stand. Not constant howling, but a few every now and then could bring them to you. Don't expect them to respond vocally, as they seldom do.
Use the weapon that fits the terrain. If you can't see 50 yards, carry the shotgun. If you can see more rifle distance, then use the AR-15.
Good luck!