I tried the trolley thing too, the only problem is finding them. Often I cant get my hands on one, so it would be a case of leaving the kids in the car while I look for one (would never ever do this) or struggle with 2 kids until I find the person that is using the baby trolley for her / his 4 year old or handbag, beat her over the head and steal the trolley. (just kidding, but honestly people using them for other things does happen ALOT) I wouldn't rely on this means of transport personally.

My tandem was a love and care from toys are us, picked it up for $199.00