The prohibition is on combinations of meat with actual dairy milk. Almond milk has a long history as a substitute, and more recently, soy milk. So long as the coconut milk contains no actual dairy milk, using it does not violate the prohibition against combining meat and milk.
There is an additional consideration that could affect your Jewish guests. If something is not actually a violation of kosher law, but it looks like it is, it is somewhere between advisory and required to take extra steps to clarify the matter. (See, for example, this article, which I hope is reasonably accessible.) In the case of almond milk, historically rabbis called for including some actual pieces of almond in the mix as an indicator. In modern times, I was once at a meal where those fake "bacon bits" were served as an optional salad topping -- and they were brought to the table in the original packaging with the kosher certification mark, not in a bowl. (Miss Manners might not approve, but rabbis would.) The article I linked suggests that when knowledge of a food is common, one needn't include the extra labeling. I would think that, in your case, it would suffice to tell people that the dish is made with coconut milk and not dairy milk. (I am not a rabbi.)
There is one more consideration, though it's about kashrut in general and not about dairy alternatives. There is a spectrum of observance levels when it comes to kashrut (or any other matter of Jewish law). According to the strict law, the beef must have been slaughtered in a particular way, processed ingredients require a type of certification, and the utensils you cook the food in matter. Some Jews consider it sufficient if all the ingredients are of the right type -- they'll eat kosher species that weren't necessarily slaughtered according to Jewish law, and/or they'll use ingredients lists on packages in the absence of the certification mark, and/or they don't care what pots you used so long as they were clean to begin with. The only way to know is to ask. Anecdotally, Jews who keep some level of kosher are used to navigating these matters, so if you make it easy for them to know what's in the food you brought, you should be fine.