Hi,
If you are planning to go up the Eiffel Tower, I recommend that you buy tickets in advance on the ET website, to save a long queue there. You can buy tickets up to the 2nd floor, or to the summit, which requires taking a second lift. Many people say that they prefer the view from the 2nd floor, as you can see more clearly. There are toilets and cafes on the Tower, so not a problem with kids. It is also quite interesting walking down from the 2nd or 1st floor through the construction framework and not as hard work as walking up! The Tower lights up and twinkles for about 10 mins on the hour after dark until about midnight. A great place to watch this is from Trocadero for a super view, or from the gardens with fountains below. Many people gather here after dark. Nice place to sit and have a picnic during the day as well. There is a small carousel nearby.
The Louvre can be interesting for kids if you just see certain things, like the Mona Lisa, Venus De Milo, and the Egyptian rooms, as most children enjoy looking at mummies and the painted mummy cases ( sarcophagi). There is a cafe and restaurant inside the museum.
There are some nice parks in Paris with things for kids to see and do, away from busy tourist areas. Some have kids playgrounds. There are extensive gardens beside the Louvre called Jardin De Tuilleries, which has a boating pond, and also a big wheel similar to the London Eye. At the far end of these gardens is Place De La Concorde, with the Egyptian obelisk in the centre. The Champs Elysees leads from here, all the way to the Arc De Triomphe, but it is quite a long walk for little legs.
It is worth going to the top of the Arc De Triomphe for fantastic views, including all the traffic on the roads branching from it. You can climb the steps to the top if they are able, or take a lift. Queues here are usually far less than at the Tower, and you can see the Tower from the top.
Another interesting climb is up the Towers of Notre Dame, but there is no lift here. This is very popular, so best to arrive early. There is a gift shop on the way up, but you go back down the other Tower, so buy any souvenirs on the way. You cannot bypass the queue with the Musem Pass, there is one queue for all.
Riding on the Hop On/ Hop Off open top buses can be fun and they stop at the main sights. You can also use the HOHO Batobus ( boats ) which also stop near main tourist sights, or take a one hour round trip on one of the sightseeing boats which have commentary in English. You can also do this at night.
Ile St Louis near Notre Dame is a very pretty Parisien area, and where you will find the famous Berthillon ice cream shop.
Les Invalides/ Army Museum may be interesting for boys, and this is where you will find Napoleon's Tomb.
People on the Trip Advisor Paris forum can help you more, as I am no expert on Paris.
It is a shame that you don't want to spend a day in Disneyland being so close, and with kids of the right age, but that is your choice. Queues and crowds there would depend on when you are going.
If you change your mind, we can help you plan your day on the TA Disneyland Paris/ Marne La Vallee forums.
Hope you all have a wonderful time.