There is just the thing here:
The free mini-series will give you plenty of game ideas and a story.
The games are written for small classes though, of up to 20 children, but if there are two adults you can always make two groups, or play as one group as there will be two of you to keep on top of the class discipline side of things. (It is better to split into two groups for many of the games though so the children do not have to wait long in between turns.)
As it is the end of the day I would use ten minutes of movement and ten minutes of quieter activities. The children may be becoming restless after a full day in school so some more playful learning games would be best, and plenty of songs such as Head shoulders knees and toes, Old Mac Donald and Ten Green Bottles.
All the best