Charades for the verbs Hide and Seek for the preps Chinese Whispers for the preps
Sparklebox will have lots of visuals that you can make flashcards then they can play snap pairs, go fish etc together.
Get a 2 copies of the same book, one with busy active scenes, I am think a Usborne series one. Have one child-without telling the other child-decide what they are going to descried- ie the duck- but they CANNOT say duck so they willl be saying things like- They are next to the boat, the are not beside the boy playing football etc...
Or good speaking/listening/ concentration skills game. Draw a scene or random set of different shapes scatter around a page then describe in terms of prepositions.
e.g. draw a large square. Beside/ next to/ on the left/ on the right, draw a small triangle with a spot in the middle. Below/ under/ beneath the triangle draw a stick man with a lollipop in his right hand. etc etc. They then compare their picture with yours.
When they get the idea they can draw their own picture and describe it to a friend. Difficulty can be added by giving 2 or more instructions at once.
I play games like this with my hearing impaired pupils- they think it's great fun.