In reply to 0153453:
If you want a lower level day lot of nice options in your range in Glen Nevis 3 Pines, Styx Buttress Right Wall are nice VDiffs and the Gutter (Diff) or Secretaries Direct (Sev).
Most of the rock climb on Ben Nevis are quite long and committing but if the weather is good they are great (watch out for loose rock if you are used to shorter or less mountainous venues).
As Jamie says Curved Ridge and Aonach Eagach may be good warm ups for Tower Ridge. Much of it is easy but there a few spots where a rope will be welcome and being able to transition quickly from pitched climbing to a quicker system of movement and back again (and knowing when it appropriate for your party to do so) will make your day faster.
Enjoy.