Stations sound like a really good idea, but to further maximize your time try the following:
1. Pre-select 3 activites before the group arrives. Students vote on 2 activites. This motivates students to focus on one game/activity and then play their second choice before its time to go back to class.
2. Use a timer (red visual is my favorite) to give younger students a time frame for the start and end of therapy activities and/or speech therapy. The students know activities must be completed before receiving a reinforcer/reward at the end of speech therapy.
3. Consider rearranging the materials and furniture in your therapy room. The students should face a dry erase board, ActivBoard or target visual displays during therapy.
Hope these ideas help.