In reply to neilwiltshire:
Next step up from Little Tryfan is definitely Milestone, a lot of the clients I've taken on Little Tryfan have found Milestone to be fairly similar, but feel slightly harder and more mountainous. It's an easy approach, and the descent is a lot easier and more suitable for you than the descent from Idwal Slabs. As for specifics, start on Pulpit Route and then do Rowan Route. For a challenge, you could do the first pitch of Direct Route, then join Rowan route to the descent. Avoid the final pitches and descend below Ivy Chimney. You can get to there in between 2 and 4 pitches depending on where you choose to belay.
After you've done a bit on Milestone, a day on the slabs will be much more enjoyable and probably the next logical step up for your wife. Route are generally 4-6 pitches and feel a lot longer obviously. The descent can be tricky, especially if you're with somebody who isn't too confident.
Check out my post here if you want to hook up:
http://www.ukclimbing.com/forums/t.php?t=615432&v=1#x8044693
I'd be happy to show you some of the classic VDiffs.
Mike
Post edited at 15:12