Fill a bowl with lots of different textured toys from around the house and add water. Freeze it. A day or two later pull it out, give the kids squirt bottles and preferably "pretend" screw drivers, I obviously like to play with fire and handed out real tools, and then let your kids at it. Jaylee was filled with questions, but Aidan was just pleased I was letting him use water, hammer and dig all at the same time. The best part, they STILL are not done with it. Another bonus, crowd free.
How do you finish off this kind of day? Let the kids stay up until 11:00 for a fireworks show like no other, wrapped in blankets on our ROOF! I might live in the ugliest building in Paris, but it has one of the best views around.