I'm considering buying a secondhand double pram (side by side) so we can exercise more easily with both our girls.

We have the City Select which we love but it's not really designed for exercising (fast walking). DD1 is 16kg and DD2 is 11 so although they're still within the recommended weight range for the Select, it's getting difficult to push them both even with DD1 in the top seat.

So any recommendations?