i brought a double pram and my dd is 3yrs 4months ds3 is 2yr 2months and ds4 is 11months 2 weeks and some days i put dd and ds3 in the double pram (i brought a baby jogger city mini) if i know she is going to be a pain and i dont have time to let her walk or sometimes she goes into the carrier and i have ds3&4 in the pram im waiting for my glider board for the pram i used one on the stroller when ds4 was first born and she loved being able to stand up but would at time jump off
if you know your ds will get tired on a long day out or you want to some walking and your ds wont walk the whole way i would get a double