My father who lives afar is coming to visit my family for a short time. If I remember correctly, he doesn’t always say brachos, sometimes doesn’t say the correct brachos. When he does say brachos, its quite quick/slurred and I’m not sure if they are considered proper brachos. Is there anything we should know about how to serve him food?
You should serve him regularly, but have in mind that you are doing the special mitzva of Kibbud av v’em. The gemora (Kiddushin 30) says that when a child honors his/her parent H-shem says that it is as if they honored Me. Therefore remember it is like having the zechus to serve food to H-shem Himself!
You do not have to worry, that he might forget to make a bracha, say it slurred or make other mistakes, it isn’t lifnei iver, because he might just do it correctly, and even if he doesn’t, he might still be yotza the bracha b’dieved. So don’t worry about that. just stick to your job and give him the best service you can.