wld i be able to use the smaller one for two?? in about 3 weeks we are going to get abby an older brother. abby is 6 mo and weighs 3.3 lbs. Jack is 2.5 years old and weighs around 7 lbs (i thinkkkk) do u think i can get away with having the small one? I have an altima coupe and i dont think theres enough space for the big one |