Should I avoid meat broth when cooking for vegetarians?
People choose to eat vegetarian diets for a number of reasons. Not only might the flavor offend your guest, but it may cause them to be physically ill.

You can substitute vegetable stock or broth for the meat products you are accustomed to using.

Mushrooms lend a meaty flavor to dishes they are used in and could potentially be used to replace your meat. I would suggest cooking them separately first to draw out the moisture, then adding them to the beans near the end of the cooking process so they soak up some of the flavors and have a chance to marry. Remember mushrooms are little culinary sponges. They will take flavors and run with them, adding their own earthy notes in the process. Search for vegetarian rice and beans dishes to get an idea of the possibilities here. 

From an etiquette standpoint, you may want to avoid the temptation to apologize to your other guests for having to make a veggie substitution as that would be a quick ticket towards alienating your vegetarian pal. I only mention that because some people don't think about things like that and I have a few friends who are on restrictive diets. They are sometimes embarrassed when people go out of their way to make menu changes for them. 

Another alternative altogether is to find a way to prepare two versions of the dish. Meaning, you could use meat as you are accustomed to but leave a portion of the food vegetarian. When it's practical I like this option a lot. It just comes with the downside of increased cleanup and stovetop logistics issues.