Help! London, Paris and Rome transportaion

Your question is hard to understand - is it advisable to buy WHAT to save money? Are you asking about passes or tickets for public transportation in those three cities?

I have the same question Kathleen did about your post.
Please clarify your question so we can help you.

is that 4 families, each with three people - does your group consist of 12 people?

buy what?

Oooops sorry missed some words there. Yes it is for public transportation in those three cities for just a family of three. Thank you.

njc, yes, but you still don't say what you are thinking of buying for public transport in each of those cities.
Each city has its own public transport system, with different ticketing systems and prices. There are sites out there on the web with pages of information for each city about transport.
Sorry, but you have to be more precise what you are asking whether it is advisable to buy.

For London, I would start here: https://tfl.gov.uk/travel-information/visiting-london/ which is the official London Transport site.
For Paris: http://www.ratp.fr/en/ratp/c_21879/visiting-paris/

Yes, the transportation cards in London, Paris and Rome will save you hassle, time and money. You'll not only be able to use the public transport system without the need to change money, get in line to buy tickets, etc but some offer free admission to attractions just by flashing your card. In Paris, for example, the card covers 60 attractions including museums. Go ahead and order them online. Here is where to get them.

(1) London- www.londonpass.com/london-transport/index.html

(2) Paris- www.parispass.com/how-it-works/paris-visite-pass.html

(3) Rome- www.romeandvaticanpass.com/rome-transport/

Terri, those sites you posted are not that actual official sites of the transport operators in each city, they are resellers (travel agents). The official sites are:
For London: https://tfl.gov.uk
For Paris: http://www.ratp.fr

And the original poster hasn't told us what they are thinking of buying, it may not be "transport passes".

njc, What are you actually wanting information on buying? Please come back and tell us.

Do you have Rick's books for these cities? For each one, he has excellent summary of your transit ticket options, including whether a pass that includes museums and transit is a good deal or not.

The specifics of what would be best for each city depend on:

1. How long you are staying, and what days of the week. For instance London and Rome have a deal for a week, which can be any consecutive 7 days. Paris has a deal for a week, but it is only for Monday through Sunday.

2. Exactly where you are staying; some locations mean more transit will be used compared with other locations.

3. What activities you are planning to do in each city. In London, there is a two for one deal on attractions that you may benefit from, but it requires the purchase of very specific transit tickets. In Rome, the Roma Pass includes transportation and free/reduced admissions to attractions; it can be a very good deal, or a waste of money, depending on your plans, the duration of your stay, etc.

4. What are the ages of the 3 of you? Specifically, for those under a certain age, they may be eligible for child fares (or if they're really young, free travel). Again, each system defines the ages for discounted or free travel differently.

So, you'd do best if you first look at Rick's books. Then, if you still have questions (and it isn't always easy to figure out the best deal), post the specifics of your situation for each city, and we can give you advice.