Give her a Credit Card with a large limit available and your blessing to use it and ride all you want...

Don't ask her what she spent until you get home.

I took my ex-wife to Greece, spent a lot of time fidgeting in jewelry stores while she hemmed and hawed about what she wanted. It was 13 years ago and that's all I remember about that trip.

Just make sure to save some time for her in the afternoons/evenings and take her to some nice restaurants (maybe suggest a spa while you are riding?).

She will probably enjoy the catherals and museums more without you (she knows you don't enjoy them even if you don't complain).