L.B.
No-Cry Sleep Solution has a chart for what number of hours babies should sleep by age, including naps, and number of naps per day.
I've read in several sleep solution books that you shouldn't keep a child up who's tired. This actually causes sleep disturbances.
Is there any way to let your baby sleep a little later in the morning? Maybe just wake your older child, help that one to get ready, and then wake your baby at the last minute for a diaper change, and give him a little snack that he can eat safely (that is choke-proof) in the carseat? You might even find that if you do it gently enough, you can transfer your sleeping baby to the carseat with little waking. Or else can you gradually get him accustomed to going to sleep a little earlier? My daughter used to go to sleep as early as 7:00.
About his naps, I think that since he's an older baby, one long nap sounds about right. It's also helping him to make up for the early waking. But it sounds like mornings might be a little more tantrum-ridden and less fun for you both, with him being tired! It's hard for a child to focus and stay calm through frustrating moments when stressed with fatigue. So, by adding another half hour or hour to his night's sleep on either end, either morning or night, you might find that a bonus is more peaceful mornings and more fun with your baby :) I know my daughter is a lot happier when she has had a good night's sleep. I really see the difference!
Hope this helps.