Eating more on training days than on non-training days is fine. It generally helps keep fat gain down a bit because you are not eating quite as much excess on non-training days when activity is low, and you're using the extra calories to build back what you tore down during workouts.
However, it can also impede on recovery a bit, say if you train in the evening and only get a couple meals in afterwards before you go to sleep--this is something I can't prove but believe however. In any case, it won't be a "make or break" detail so don't worry about it for the foreseeable future!
IF it does impede recovery, it won't be by very much at all unless you're really really working insanely hard as an athlete or truly advanced trainee.
So, go for it. I like the idea for remaining relatively lean as you bulk up. However, I would use the majority of my carbs at breakfast and in the meals right after training, on training days. I would use MORE fats and LESS carbs on my non-training days, because carbs have a tendency to cause insulin spikes which can lead to a bit more fat storage if not used in short order. Fats not so much.
Re: walking a lot. Don't even worry about it. It's a good thing not a bad thing. It's not strenuous and doesn't eat up a ton of calories and it will keep you leaner through increased activity. Unless of course you're hiking mountains. Then that can be much more demanding calorie wise. Otherwise don't sweat it.