Starting my baby registry with baby #3

I kind of want to start fresh with everything. We can afford it this time 😌 I have a question though.. baby #2 is not even 2 years old and my oldest will be 4 when baby arrives. What kind of stroller should I get? I definitely need a two-seater but sometimes my oldest likes to sit as well. Is there something that fits 3? Should I just tell my oldest to walk now?