DD playing outside the garden, and what to do with DS?

[RedHotPokers]

A lot of children in our street play outside (in the street) with each other. They probably range in age from 4 or 5 to about 10, and all play with each other in a road that does have a lot of parked cars, and can have some traffic but nothing too busy or fast.

DD (nearly 5) has never asked to play in the street, and mostly just plays with her little brother (2.3yo) in the garden. However, every now an again she seems curious and peeks out the gate to see whats happening in the road. I have never really discussed it with her, and don't know whether to ask her if she wants to play with the others and make some friends, or just leave it.

I am a bit worried about her playing unsupervised (I can't see the road from our house - big fence) but she is fairly sensible so it should be fine. However I am more worried that DS will be inconsolable if DD is playing in the street and he is stuck in the garden. He is way too little to be unsupervised, and me standing in the road for ages would be a real PITA.

WWYD?