ryancanada,First of all, welcome to the Boards and congratulations! I have a few comments and questions.
First the questions....> When is this trip taking place?
> Is there any possibility of extending the time a bit?
> What kind of a budget are you working with?
> Have you booked air tickets yet?
> Are you planning to pre-book accommodations?
> Have you purchased Backpacks yet?
> Do you both have Passports? Have you checked the expiry dates? Will your bride have a Passport in her married name at the time you travel?
Now the comments.....I'm considerably older, so my trips are not quite the same. However, I do stay in Hostels on occasion and I do use a Backpack.
In planning your time, keep in mind that you'll lose the first day in flight times and time zone changes, and will arrive in Europe the day after you departed. The last day will be spent on the flight home.
As you haven't travelled in Europe before, I would
highly recommend reading the Guidebook
Europe Through The Back Door before you get too far in your planning. It will provide a lot of good information on how to travel well in Europe and avoid problems. Read the "Rail Skills" chapter carefully!
Your idea of using open-jaw flights is great (inbound Venice, outbound Paris). That's the method I always use.
As you'll be staying in Hostels most of the time, you might consider taking out inexpensive memberships in
www.hihostels.com. That will provide preferred booking and slightly better rates over non-members. They have properties in most places in Europe, and I find the facilities are usually fairly consistent.
However, in Rome I'd recommend staying in a non-HI Hostel. Check
www.hostelsalessandro.com/en/palace for prices and room information. It's located an easy eight minute (or so) walk from Termini station, and is very modern. They do have double rooms available, but they're about the same cost as a budget Hotel.
Concerning the cities you want to visit....> Venice - 2 days should be adequate, but plan your touring well! You'll need a few days to get over jet lag. You may find Venice a bit "pricey".
> Croatia - you indicated 3 days at a Festival. It would be a good idea to return to Italy right after the Festival, as you don't have time for much touring in Croatia. I wouldn't bother stopping in Venice after Croatia - go directly to your stop in Tuscany.
> Tuscany - that's a fairly large region. Which places do you have in mind? You could consider a 2 or 3 days in either Florence or Siena.
> Rome - I normally suggest at least five days, but with your time limit you may have to settle for 3 or 4. Plan your touring carefully.
> Genoa - I'd skip that and perhaps substitute a day or two in the Cinque Terre.
> Nice - I'd suggest at least 3 days here as it's a beautiful city and lots of possibilities for day trips. A day trip to Monaco is easy and as I recall the Bus is only €1 each way. When you arrive in Monaco, you can either hike up the hill to the town and Castle, or take a Bus but that means another €1. The Changing of the Guard takes place at 11:55 and you could also visit the Church where Princess Grace is interred. It's VERY quick to get from Nice to Paris via TGV, which travels at 300 kMH.
> Marseille - I'd skip it. I don't believe you have time and it's not really that special.
> Paris - as with Rome, at least 4 days as there's LOTS to see! You may consider a
Paris Museum Pass, perhaps a two-day version. It will get you through the queues a bit quicker. Which locations are you planning to visit in Paris? Which area of Paris are you planning to stay?
One other point regarding Paris. When you head for the airport for your flight home, there are several methods for getting there. One of the easiest is to take the Metro and then RER "B" (I believe it "splits" into two routes at the end, so be sure to use the correct one). You could also arrange a Shuttle or take the Roissy Bus. Check
parisbytrain.com for all the details.
You'll need to allow for travel times also, as each time you change location will require at least half a day (and sometimes more).
I'd suggest checking your local Library or book stores to have a look at Guidebooks for Italy and France especially. They will provide you with a lot of information on sightseeing options, transportation, and other details for each of the places you'll be visiting. I normally pack along one or two country Guidebooks, as they're valuable for reference during trips.
Be sure that both of you are wearing Money Belts, and be vigilant for petty theft and pickpockets. They're VERY skillful in Europe!
Finally, do you have a PBS TV station in your area? You might watch for
www.ricksteves.com/tvr/tvr_menu.htm as it may provide some ideas on sights to see in each city.
Good luck with your planning.