okay, if at the moment you're only expected to plan some activities think about the resources that the setting currently has and how you could one of them differently - water, sand, playdough, paint, bricks, balls, books, puppets, paper, small world animals?
Unless you've been given a budget to buy resources you'll be expected to use what's already in the setting or what the setting actively recycles - cardboard boxes that could be springtime bird nests or yogurt pots for flower vases?
Activities are identifying, sorting, matching, building, listening, talking, smelling, touching, tasting, watching. More physical/locomotor whole body activities are running, stopping, dancing, jumping, bunny hops, throwing, kicking and catching. and fine motor skill activities include scissor cutting, cookie cutters, painting tools, drawing tools, sorting/transfer tools - spoons, tweezers, pipettes
Once you know what each of your children are enjoying you can start to plan activities based around them eg, for a child interested in driving cars, small or sit&rides, use blank pieces of paper, sticky tape & crayons and build roads with them. Maybe make it into a shape - circle, square, triangle and count the sheets of paper as children mark make freely on them.
Use a puppet at the sand tray to encourage bucket filling, turning out, using language such as 'how many' 'which way' fill, full, empty.
A bed sheet makes a good ball toss taupe that all ages can enjoy working together on.
Mix flour and water to explore dough (shameless plug sorry, how about making a batch of not-recommended but edible
fibre slime with
spring themed sprinkles)
Use
box templates or envelopes for decorating & hiding/concealing
Use
stand up bags with coloured paper monsters stuck to the front and sort bricks - 'this hungry monster eats blue bricks'. Have the bricks in a bag and explain the turn taking rules - maybe say how one/two/three bricks can be removed from the bag on each go?
For spring maybe use green playdough, craft stems, paper leaves and artificial flowers and build a meadow/collage activities, name and identify plant parts - stalk, leaf, flower, petal. Use pompoms for rabbit tails and paper straws for whiskers. Make bunting for a display board?
Use storyboard folders to tell a tale - pull a character from the folder, introduce it and then take out another piece to build a story, not necessarily in any order as you'll want the story to change each time its used.
Practice threading skills by feeding
lengths of ribbon into bottles - satin, grosgrain & string all have different textures
Use
grip seal bags with a squirt of ready mix paint inside for mark making & paint moving activities. Write names, draw faces - add a spoonful of powder paint or glitter to change-up if it's an activity that happens often.
If it helps there's a
preschool activity planning sheet and child development planner on this thread.
It is a big responsibility
and I'm sure you wouldn't of been asked if your boss didn't feel you were ready. Just remember activity planning isn't ever a competition between adults and it sounds as though all the children will continue to benefit hugely from joining in with each other :)
I hope this helps a little