At this age most children are very involved in the world of pretend play and start developing stories using simple props at home. You are a lucky parent if your older child wants to spend time with the younger sibling. In fact by spending time with the older sibling, your little one is going to learn a lot. Many physical activities which as parents you might not encourage your 2+ year old to do, will be very easily picked up by observing the older child. Your older child will work as a motivating factor for the younger child to try out new things on the playground. In fact it is mostly observed that children who have an older sibling have better gross motor skills than a single child their age.
What you need to know
If your little one has an older sibling who is willing to play along then their level of development is much faster. Look for activities outdoors that both your children can participate in and enjoy. You can also prepare a backyard obstacle course challenge that has varying degree of difficulties for both the kids. Simple games like catching bugs, ball kicking, bike riding etc are activities that are fun and learning for both the age groups.
Time spent apart is equally important
However much both your kids enjoy spending time with each other, you must make sure that they spend enough time away from each other and with children their age group. This is important not only to avoid resentment but also from the development point of view. The dynamics are vastly different when playing with their own age group than when playing with an older sibling. Interacting with peers their age gives your younger child the confidence and comfort of their own skill levels.