Looking to do a cruise for the first time. We are looking at Celebrity Equinox, NCL Epic, and Royal Caribbean Allure of the Seas visiting the Med next summer. I know Celebrity is supposed to be the nicest of these cruise lines. Here are some things about us any suggestions of which cruise line might be the best for us?

We are late 50's and enjoy life but not huge partiers anymore but enjoy some entertainment or shows in evening.

We have never cruised before not sure what size ship would be best.

Really prefer casual to glitzy...hubby really doesn't want to haul a suit or tux and I am not into ball gowns.
Is there anywhere you can eat on the formal nights that you can dress casual or will that have to be a room service night?

We enjoy a cocktail, but not constant drinkers, how expensive is a beer or rum and coke on board if you don't buy a package.

Shore excursions...we have always done our homework and explored on our own. HOWEVER we have not been to Europe and wondering if this is advisable or stick to the shore excursions that you pay for in Italy, etc.

Is it better to book air through the cruise line or on our own...same for hotels before or after cruise?

Thanks for any and all help. I know I am comparing apples and oranges probably but trying to get a feel for this.