I have a D5100 as well with a standard lens.
The tele-lens is a Tamron AF70-300 F/4-5.6 DI LD Macro 1:2 - so, quite similar, however, the D5100 requires a lens with build in motor to utilize AF.
For me, I do not trust AF for my type of shooting, so this manual operation is just fine for me. Now for the Macro function: I can switch to it between 180-300mm which gives me some distance from the subject which works like a treat as you need a sturdy tripod anyway (got an old Mamiya one, you could strap a donkey on it) and this requires some space = distance due to the spread legs.
As an additional measure use an achromatic (close-up) lens of very good quality, remember Macro equals (normally) crisp details.