as far as the carpets,, can you put plastic under the seats incase of accidents? just a thought. we have hard wood floors so i'm not sure this would be any good or not.
as far as training them at the same time.. i have two that are 9 1/2 months apart and thought about doing that with mine. a girl and boy. but after my son just one day said he wanted to wear his big boy underpants at 3 years and 5 months and was trained pretty quickly..i realized i didn't want to have to do this with two kids at the same time.
i went to this womens Christian conference that Bobbi McCaughey spoke at. she is the lady that had the septuplets in des moines.http://en.wikipedia.org/wiki/McCaughey_septuplets
after she spoke you could ask her questions. i asked about potty training so many kids at the same time.. she advised that you do one at a time, since most the time they won't be ready all at the same time and for your sanity as well. lol
i would follow their lead. my son was trained in a weekend because i believe he was ready and he let us know it.
we had had practices on and off before this time. and we talked a lot about wearing his big boy underpants and how exciting that will be etc. talk positive about it. don't make a big deal about accidents. teach them sitting down first.
let them create their own little potty rituals.
with my son he would sit and read a book or two. my daughter who just turned 3 in november finally let us put her on the potty around christmas after getting her the big girl potty book. before that she would scream and fight us. so we didn't put it. then all of a sudden she was wanting to sit on it and was going. she's still a bit from us going gung ho with the underpants and such.. but she does tell us when she has pooped and that she wants changed. i think every child is different to when their bodies can tell their brains BEFORE they have to potty. so i wait for those Q's
good luck.. don't think you are doing anything wrong is you don't get them done at the same time. if they are both ready and willing.. awesome!!!!