Rikai is a great dictionary for translation, but translating dictionaries should only be used if there is not enough time or context to figure out the meaning of a word. Ideally, you should go to an English-only dictionary and use the bilingual dictionary only as a last resort.
So get your students away from bilingual dictionaries by using an online English-only dictionary. Not one with just text, but one with graphic representations of meaning. I’m talking about Visuwords.
Enter a word into the box, and a whole sematic web appears below. The connections are coded and you can move them around, get definitions by hovering over the words with the mouse, and use it in many different ways. People remember vocabulary by connecting a word to other words. Trying to remember words in a list is one of the worst ways to learn new words, second only to flash cards. Lists and flash cards help you to forget words. Using words in sentences and linking them to other words is the way to build a vocabulary. This tool works like your brain does.