This is the perfect way to do it. Some games are built around the concept of achievements better than others, and nothing annoys me more than:
1) *Starts new file* = Achievement unlocked!
2) *Gets through tutorial* = Achievement unlocked!
3) *Gets to second level* = Achievement unlocked!
Those aren't achievements, they're ways for insecure gamers to feel better about themselves with bloated gamerscores. The other 99.99% of gamers don't give a crap about these stupidly placed achievements.