What are you looking for? Play equipment recommendations or fun activities?
Things like toddler slide and pop-up tent and tunnel keep little ones amused but they grow out of them fairly soon.
If you want something big, a trampoline is fab and will be ages before they grow out of it but 2.5 might be a little bit young for one yet.
Paddling pools are good. If you are worried about safety or have difficulty filling it or can't afford the water, you can still have water play. Fill a washing up bowl with water and provide lots of plastic containers - yogurt pots, strawberry punnets, funnels etc.
Outdoor painting is great as well. Get bit sheets of paper or wallpaper rolls and do hand and foot painting without needing to worry about mess.
If you have paving, get some chalks to colour the paving in - it will just wash away when it rains.
Growing stuff. A bit late for planting most seeds now but you could probably find a few quick growing things like lettuce and radishes. Or sprout beans on wet kitchen paper and plant them. Kids love watering stuff!