Maggie, 

I think we need to narrow down the prospects slightly. There are tons of different day trips. What is appealing to you? There are day trips that leave very early in the morning and don't get back till late at night. Are you interested in any of them? Or do you prefer trips that take less time. 

As for restaurants. Is the sky the limit on price too? What sort of places do you like? Ethnic? Irish? Will the restaurants be in a certain area of Dublin?

Take a look at a few websites: 

Day Tours

Railtours

Restaurants

Dublin Restaurant Reviews

Menu Pages Reviews

Michele