we 5 persons so we will have 5 big suitcase
I plan to travel light every single time, and I end up with a big suitcase every single time... so I can understand how this happens. However, traveling with five people and five suitcases is a bit different from traveling with just two people and two suitcases!
O.k., and now I am going to have to do a lot of disagreeing. :-)
So you will need something like a very large sedan or even a small
van. That can get expensive. One alternative would be to use the
train/bus for point to point. Once there, hire a local driver or taxi
for the day or half-day who could drive you around
I am sorry, but that doesn't make any sense to me. This calculation might work in some low-wage countries, but have you ever tried hiring a local driver or a taxi for a day or half in a country like Germany? You can probably rent a van for four weeks for what that half day would cost you.
However, all trains have large luggage storage bins that will easily
accommodate all of your large suitcases.
Certainly, and then no one else in the train car is going to have any room for their suitcases. People are really going to love you if you enter a crowded train and use up all the storage space that is meant for everyone for just your party. More likely though, you'll enter the train and find the storage racks packed with other people's luggage already, with just enough space left to add maybe one or two suitcases. Then what?
Someone might grab a backpack or a small carry-on but no one is
grabbing a large, heavy suitcase.
Sorry to disappoint you, but I've seen it happen. I always keep an eye on my luggage at least during stops.
Trains are frequently with lots of capacity so you can easily obtain
tickets when needed.
He/She is going to be traveling in July/August. That's the main vacation time in many European countries. Trains are going to be packed.
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Having said all that, I would nonetheless recommend going by train and not by car, especially if you are going mostly to big towns that have good train connections and limited parking, for one very simple reason:
i don't like driving
If you are not comfortable driving, you'll hate driving in a foreign country. You are going to be totally stressed out instead of getting to relax and enjoy your vacation.
Do your research on good train connections and on the dates of school vacations of the countries you will be visiting. Avoid traveling on days when school vacations begin or end, or on the weekends of public holidays. Make seat reservations.
Most important though: Get a good guidebook and find out what you want to see, or at least do some research on Wikivoyage for starters. Excuse me for saying so, but your current itinerary seems kind of clueless, like "we want to see all of Europe in 41 days but don't really know what we want to see". What are you interested in? Tell us, and we can also give you a hint or two.
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There is one alternative that you should consider: Book a tour.
You won't have to do any driving, and your luggage will be taken care of. And the tour guides know where to take you so you won't waste your time ending up in places that aren't really that interesting.