The Eiffel Tower is currently surrounded by wire fencing and soldiers are out in force. There's no guarantee - either due to weather or overcrowding - that you can get access. There won't be a fireworks show at the Eiffel Tower.
There will be a lot of people milling around, trying to sell champagne and trinkets - and pickpockets.
Most people head to the Champs-Elysees, where there are barricades and soldiers, but at least you can mingle with like-minded folks. No glass is permitted at either the Eiffel Tower or the Champs-Elysees. Be prepared to walk back to wherever you are staying.
There might or might not be a small light show at the Arc de Triomphe, but this hasn't been announced yet. There will be no fireworks.