There isn't really an answer to this question unfortunately. My first child loved the car seat, my second child didn't. She screamed constantly while in it.
My almost 3 year old never liked it and rarely slept in it. Even now. We drove 26 hours in the car earlier this year, a good portion at night, and she slept 5 1/2 hours total. Once we switched to a convertible car seat (around 10 months old) it helped some and being able to have snacks when she got older helped more, but she still does her fair share of fussing in it. My current baby (9 weeks), sleeps great in it and usually just watches out the window quietly when not sleeping. They act similarly though outside of the carseat as well. My 3 year old was always more of a screamer, up multiple times a night, virtually impossible to put to sleep. She also has only fallen asleep 4 or 5 times in her entire life that did not involve us intentionally putting her to bed/sleep. Has never just napped on the couch or fallen asleep when playing or when out and about. My second one so far falls asleep no problem on her own and is just very content. Some kids are just more challenging when it comes to all things sleep and travel.
My baby likes to look at herself in the mirror I have strapped to the headrest so that I can peek at her from the rear view when I'm driving. It calms her. Also, when I put her in the seat if she cries I just swing the seat and she calms down.
Thanks for all the input! My sister also suggested kids music and I remembered he likes Dave Matthews Band. Also, she said shaking and crinkling a bottle of water worked for them. I'll be sure to give all of these a try on our long trip this weekend!
My kid HATED the carseat until she was about 3 months old. She would scream the whole time she was in it, and would not sleep. Now, if we stick her in there and it's close to nap time, she passes out almost instantly. Though she will occasionally fuss right when we strap her in, as soon as we are on the move she quiets down. If we don't anticipate her sleeping, we give her a couple of toys to play with and she's usually quiet.
Re: Tricks for carseat + 10 wk old