A few points to mention (you may already be aware of these).......
- like most other European budget airlines, easyJet is quite strict with carry-on luggage. With the cheapest seats, only ONE carry-on item per passenger of the approved size is permitted. It sounds like you've paid for advance seat selection, so that may allow a bit more latitude (I haven't checked for awhile).
- especially with the children and a 70 year old, paying for Speedy Boarding would be a good idea. I find that boarding first is a benefit, as that allows one to board and get some space in the overhead bins before the "horde" arrives.
- as you're driving in Italy, note that each driver listed on the rental form will require the compulsory International Driver's Permit, which is used in conjunction with your home D.L. IDP's are valid for one year and easily obtainable at any AAA / CAA office for a small fee.
- be sure to also do some research on the topic of ZTL (limited traffic) areas, which now exist in many Italian towns. EACH pass through these will result in hefty fines, which you may not know about until several months after you return home. DO NOT drive in Florence as the city is heavily covered with automated ZTL cameras. You may find this helpful - http://www.slowtrav.com/italy/driving/traffic_cameras_speeding.htm
- there are also some potentially expensive caveats to be aware of when using public transit (Metro, Buses) in places like Rome or Paris. Tickets must be validated prior to use, or again hefty fines are possible, and those will be collected on the spot! If using the Paris Metro, you must retain tickets until you've exited the system. Even Rick Steves was fined last year for forgetting that.
Don't discount the use of trains in Europe. Especially when using the high speed trains which travel at up to 300 km/h, they're an efficient and quick way to get around.
Finally I'd highly recommend having a look at the RS guidebooks as there's a lot of good information that will help your touring go smoothly in each location. For example, ways to beat the queues for major attractions, information on which days Museums are closed, information on hotels, restaurants, etc. Most of the guidebooks are available in E-book format at reduced cost, if you'll be travelling with a Kindle, iPad or whatever.
If you'll be travelling with any electronic gadgets, be sure to check that they're designed for "world operation" or you'll get a rude awakening the first time you connect them to an outlet in Europe. Packing along several Plug Adaptors would be prudent, as they're small and easily misplaced.