IMO I think that in one hand you should carry some pepper spray...and in the other hand, carry some treat bags LOL
seriously tho...I worry because I know a lady who was attacked by her best friends chow...a dog she was around on a VERY regular basis for 6 years. the friend left town, she went over to feed the dog and care for it and it attacked her face. MAJOR damage to her face. so I don't care how well you know a big dog, if it is not yours especially, you are better off being safe than sorry.
so really...go to ace hardware and buy some pepper spray to put on your keychain. don't act afraid when you go over there. be loving but not too playful. I wouldn't get on the floor with them or anything. I was attacked by my uncles 2 pitt mixes as a child because I got too playful. they thought I was playing like my uncle played with them
i am not one to be afraid of dogs....but like i said...better safe than sorry.
dogs can sense fear, anxiety, etc. so just go in like you are supposed to be there but be prepared for the worse....just in case it happens. know what I mean??? oh..and remember the rule of letting them smell the palms of your hands before you go to pet them or touch them
good luck