Personally I don't see anything wrong with counting on fingers to do simple add/subtract. DS does that lots of times if he doesn't remember the math fact even though he has his times table pretty much memorized through 12x12. For Easter DS got a large poster of the times table that hangs in his room. Since he's fascinated with numbers, he pretty much just learned the table because he had lots of time to look at his poster. (I got it from a local educational/learning center.) So he knows his multiplication best. Funny thing is that I can't find a similar addition poster else I'd get that for him as well. My perspective is that by doing the higher math DS gets the chance to practice the add/subtract fundamentals. Our DS too doesn't like to do simple math sheets anymore either.
Good luck!
JB
