Just edit bots.txt and put in a "funname" for each bot and put in whatever you want.
Make sure you save the file with the proper directory structure in a seperate pk3 and run it in your base folder (or whatever, for your setup).
Though technically you shouldn't need to notify people that your bots are in fact bots, since they can see it for themselves in the server status window (IIRC) or score table (how else would they have a 0 ping on the internet?).
PS: I've never messed with "bot_grapple" what does it do exactly?