What is a reasonable amount of Euro's to have when travel Europe for spending money each day including Food?

We will be visiting London, Berlin, Prague, Vienna, Venice, Rome, Amalfi, Florence, Milan and Paris
and we will be spending money on Food, Tourist Attractions and some Souvenirs

If you are traveling to European Union, you’ll need approximately 30-40 euros per day to eat, have a cup of coffee at a bar during the day, and go out at night and have a drink or two. It depends on what country are you going to, and weather you are going to capitals or smaller cities. Portugal and Bulgaria are the cheapest, and France, Germany and Austria are the most expensive ones.

a good restaurant will cost you around 20€ (if it costs less then it's crap) so count at the very least about 50€

If you're not actually hitchhiking and buying food at roadside stands, and using public transport legally, take 70€ as the minimum, and keep another 20 in your pocket just for the sake of being on the safe side. That's not including accomodation. The list of your towns are the tourist hot spots which don't come cheap. You probably won't even get a B&B for less than 50 Euros a night.

London is expensive, the cheapest bed in a hostel is 20 GBP alone. Similar is true for all major capitals except Prague and Berlin. The Amalfi coast is expensive too.

I strongly suggest bringing at least 50 EUR per day and person if you sleep in hostels and on camping sites and buy your food in supermarkets. It is possible to get by on 35 EUR per day, but this means missing meals, seeing only sights that are for free, getting around by bike or on foot and no souveniers at all.

Nice places to stay:
London Generator or HI Earl's Court
Berlin Heart of Gold or Meininger's
Prague AO or
http://www.plusvillages.com (Prague, Rome, Florence - their Venice venture is directly near the airport and suffers from noise)
Camping Spartacus in Pompeii for the Amalfi coast - easy to commute and a lot cheaper with a supermarket right down the street
http://www.campingspartacus.it/

http://www.aohostels.com
http://www.meininger-hostels.com
http://www.heartofgold-hostel.de
http://www.generatorhostels.com
http://www.yha.org.uk/find-accommodation/london/hostels/london-earls-court/index.aspx

I assume you have paid for your travel and lodgings.
Are you joining a tour?
If so, take €100 a day per person if you can afford it. You will need at least €50 for food if you go to moderate restaurants, and keep lunch costs to a minimum.
If you travel with a tour you are taken to restaurants so you often have little choice in the matter, and if you go with the group you might spend quite a bit on drinks too.
If you like to buy souvenirs, or feel obliged to buy in every place the tour visits a factory or special shop, you will spend even more. (On some tours you are taken to diamond factories that have a cheapest offer of several hunderd of Euro ;-/ )

If entry fees are not included in the tour, add an other chunk to the budget, many museums cost about €10 each for entry with a group, and you might do two or three of those on one day if you want to see it all.

When you travel as individuals you might spend less, as you can select the cheaper places to eat, (have a proper lunch and buy bread and toppings in a supermarket for dinner,) and will not do three expensive museums or sights on one day. (You might end looking up at the Eiffel tower rather than going up yourself.)

If you have not paid for lodgings and travel yet, you should bring at least €50 per day per person for hostels, food that you prepare yourself and transport, €100 if you stay in moderate hotels and eat out, add your €50 to €100 for sight-seeing, drinking and souvenirs.
So €100 for skinning it, to €300 for generous traveling. That is per person-per day, on top of your international flights.