For our twins we have a nipper, it's pretty narrow, not too expensive, very light, suitable from newborn. You'd need to check it for your boot. It goes through any door that wll take a wheelchair. It doesn't have seats that come far forward, some toddlers don't like the way it reclines slightly. I find bus drivers don't let me on with this buggy though. We also had a tandem, Jane powertwin. I don't particularly like tandems, though it does mean the children can't hit each other etc while in the buggy. It obviosuyl goes through narrow spaces. Once the new baby is a few months old, a mclaren twin side by side might be the thing, can't go far wrong with a mclaren! Then there is the phil and ted with the coccoon... I must say the underneath position doesn't look much fun to me, you'd need to consider how long you'd have two toddlers in the buggy.... These buggies fit into shops, on buses.