As Mark Twain points out in The Adventures of Tom Sawyer, any activity instantly becomes more attractive if it is presented as play rather than work. This is particularly true in the case of young language learners (generally taken to mean children between the ages of five and twelve). There are plenty of well established games that are often used to teach English: charades, last man standing, and so forth. Typing "English teaching games" into any search engine will bring up hundreds of them. However, since you will probably have specific teaching objectives, the best approach is usually to work backwards from the skill or content you want to teach.
For instance, suppose you want to teach conjunctions. For a lesson on coordinating conjunctions, you might make a list of the most common (and, but, for, so, etc.) and get the students to make up a story, with each one contributing a phrase ending in a conjunction, which is then picked up by the next student. This reinforces the idea that conjunctions connect phrases, and it also allows the students to be creative. If there are more than six or seven students in the class (as there generally will be), then divide them into two or more competitive teams. An element of competition is always effective in engaging the interest of this age group. To maintain the energy level of the class, you should also ensure that, apart from brief explanations from you at the key points, the learners do most of the talking, with your guidance and correction when appropriate.