Long-term, it seems wise to just go AWS. The difference of learning AWS versus deploying right now in Linode (if you have experienced web server engineers) is negligible. I'd say even 30-40 hours worth of learning/testing can get you up and running in AWS.
Also, you have to think about possible downtime migrating from Linode to AWS (or increasing your Linode resources) or setting up a mechanism for no-downtime.
I agree with what you say here: "go directly to AWS, take the extra time to set it up and be done with it." To me, if the initial time/resource cost is negligible (which in this case, IMHO, it is), I'm going for the permanent solution instead of what seems to be a stop-gap solution. Less headaches, more time to devote to other parts of your start-up at a time of growth where your time and resources will be scarce, and fewer things to worry about. I'd rather pay the time up front when I'm still starting out, rather than later where it will be more difficult and most probably more costly.
This applies only because you already know AWS is the end-game. Otherwise, I'd just launch in Linode first since it's quick and I (and you) know how it works already, then deal with scaling later when you actually know you need to scale.
And don't knock Linode; it can take a beating.