French classes for kids

I wouldn't bother unless you want the children out of the house. Their value will be very limited. Concentrate on settling in your immediate environment.

If there are however not going to French schools, then that is very different. However, don't expect miracles at Kiddy Classes, the standard will vary enormously.

If you want French classes, without saying where you'll be living, couldn't advise further. There are about 5 choices but you'd be best choosing the nearest.

Thanks for the tips. To clarify: my kids will not be attending French-speaking schools, but I will have to enrol them in "Stages" for most of the holidays because I will be working full time. Since there dem to be few English-language summer camps, the idea is to introduce them to French right away.

We will live in Woluwe-St Lambert 

I'm grateful for additional tips!

Indeed Kiddyclasses will be your nearest, they are in conjuntion in WSP base with Action Sport. There are more expensive an possibly better ones run by CLL in conjunction with Mikado in the same area of WSP. Take a look at them.

For English stages, the "cheapest" and nearest will be the ones run by ACE of Brussels, a new school opening in the autumn who seem to have a good business plan by immediately offering holiday stages. 200 euro per week, more expensive than French or Dutch but much cheaper than alternatives in English.

You might want to consider just any local stage, especially if you find the Action Sport/Kiddy Classes successful for you, where a whole day is with Action Sport, it's much cheaper and they have now expanded the options and locations in the WSL/WSP area. This is just an example, there are 100s of choices. Use this website to search by area, age, type.
http://www.lekid.be/