You've some great advice from Goldcircle & Littlevoices which is undisputable, I'll just add my wee bit.

I also agree that Orlando is a great family option. The LH flights from FRA on the 346's have seat layouts that are good for families and the crew are good with kids too. We flew FRA-ORD with a 18 month old and she was spoiled rotten (she's extremely cute tho ).

You could do a week in Orlando then a week on the Gulf coast and fly back from Tampa with LH.

If Florida is not your thing then consider the east coast resorts. We love the Carolina's for real old school family holidays with great beaches, great hotels, B&B's and beachfront lodges. This is where American families head in the summer as the weather is great and value for money is the name of the game. It needs some research but is easily reached as you could fly into Charlotte with US or Newark with CO then catch a connection.

Have a look here for some ideas as its a great way to see the real America rather than Florida's version.

http://www.destination360.com/north-...rolina/beaches

Have a great one!