Do you have sound machines?
Or floor fans?
Those work wonders.
Grace is a really light sleeper so we have a sound machine in her room and a fan outside her door....and we don't have any other kids LOL
Can your older kids have quiet play at least for the first 45 minutes of her nap so that she can get past the first cycle?
Grace always wakes up at the 30 minute mark...if nothing grabs her attention she'll go back off and will sleep deeply for a bit. Can that be their TV time or home work time, etc. Something more low key...outside time, etc.
A lo doesn't need to be awake 12 hours....they just usually have a 12 hour day including nap time.
And, not all lo's need 12 hours at night...some 10 or 11. You'll just have to kind of adjust according to the needs of all your kiddos.
You are doing a really great job!!!
Melissa