I don't know your child's interest. But still I will try to give you some options.
1.If your child is interested in music, you can play the game "Follow the leader".. Use containers made of different materials like plastic, glass, ceramic, stainlesssteel, copper, brass.. Tap the containers in a rhythm and make him do the same rhythm on the same object that you used. To start with you can tap on one object with a specific rhythm pattern (1 2 123 or 123 123 1 2 3).. Hope you get it.. Then combine 2 objects and start including more. He will have to tap the pans in the same order and in the same rhythm for which he has to focus and remember. It will be lot of fun to do a body movement too in an order to be followed since he likes physical activity.
2. Another variation of the above activity is to blindfold him. you tap any of the containers. he has to observe the sound and tell you which object you tapped on.
3. Play "I spy".. To start with , give a clue on the objects which are very near to him. Use simple clues. This activity improves his observation skills. There is a book series called "I spy" by Jean Marzallo and Wick. Those are absolutely amazing books for any age. The authors have used models to form landscapes or town or forest which you can't differentiate from the real scene. 100s of things are hidden in each page and it's lot of fun to find.. We have many of the books from this series.. I get hooked on these books along with my little one...
4. Change the things around the house in the way they are not supposed to be. For example place a photo frame upside down, Wear the socks on your hand and let your child find what's not normal. Set an alarm for 2 or 5 min within which he has to find.. This involves physical activity as well as observation skill.
5. Put his favorite things like animals or dinosaurs or cars in a bag in which he can't see what's inside. Let him put his hand inside the bag and feel it and tell you what he picked. Take turns to play this game
6. All kids are generally fond of water. So let him play in the bath tub or give him a bucket of water along with a containers of different size.. You will be amazed to see how occupied he is playing by pouring water from one container to other. Same thing you can do with beans or rice or dhal or even beach sand (if it's clean).. This activity helps him to sit and play in one place for a while.
7. If he likes messy and sticky things, give him natural clay to play with. Or try giving him some paints. Spread the news paper on the floor and give a big sheet os white paper and paint and make him paint with anything he likes. He can use his palm, thumb, an old tooth brush (for touching and splattering the paint), Cut vegetables, nutshells, ear bud, pieces of card board (pour a blob of paint and use the cardboard piece to spread the paint), Sponge, tissuepaper (crumpled).. This doesn't need any directions, He can create his own painting as he wants. But it will be a little messy for you clean up. You can mix white glue and tempera paint to make painting.
8. If he likes to play in sand, make an art with just glue, sand and some color powder. Mix the sand and the color. Draw a picture and apply glue and pour the sand of appropriate color and let it dry.. Kids will sit and do this for sure (esp if he is like mine who likes to play with messy stuff)..
9. Use 3 to 4 strings of different size and keep them entangled and mark one end of the strings as A, B and C. At the other end of one of the strings, tie a toy or a pencil. Make your little one find which string is tied to the toy starting to find from the ends that are marked A B and C
10. Make him find differences between pictures, complete a maze. either you can make your own or you can buy an activity book with such activities.
11. Keep his favorite things on the tray and allow him to observe for a while and when he is not seeing, take out some of the things. now let him find what is missing.
12. Make him observe a picture for a while and then ask him questions about the picture. e.g what color shirt was the boy wearing, how many flowers were there in the garden etc.. These actvities will improve his memory too.
Will add more as and when I remember the activities which I did with my kid.. Hope this list helps you to some extent.