Living

Huldenberg is Flemish, so sending your kids to school in French isn't going to endear you to the local population. If your kids are not at the local schools, you will have trouble meeting people and you will spend a LOT of time taxiing them around.
You also have to remember that ex-pats are by no means a homogeneous community, and Huldenberg commune is a series of small villages with a low proportion of non-Belgians.
Unless you're going for the 100% Flemish experience or you don't like people, look elsewhere.
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Who told you Huldenberg would be a good idea in the first place?

"Huldenberg is Flemish, so sending your kids to school in French isn't going to endear you to the local population."
...... and, perhaps more importantly, sending your kids to school in Wavre isn't going to endear them to the local Dutch-speaking kids. Perhaps you deliberately want to deprive your kids of friendships, but childhood friendships are important in Belgium both sides of the linguistic divide, so if you want to live in Flanders send your kids to a local Dutch-speaking school, they will soon master the language - and get a very different and valuable outlook on life. If you have any doubts about the quality of education in Belgium just go to any border area and watch the kids pouring in from the neighbouring country to go to school in Belgium rather than their home country - it's quite an eye-opener.

I'm inclined to agree with the others. If you're planning to have your kids in school in Wavre, then you would be better living in French speaking Wallonie, rather than Flemish speaking Flanders.

Flanders is Dutch speaking.

What the heck is expat movement? Sounds like some rare form of digestion process.

Not only is Huldenberg Dutch-speaking but it is close to the linguistic frontier and is governed by a CD&V-NVA coalition, so you can expect to HAVE to speak Dutch when dealing with officialdom. Officials may be able to speak English but are likely to have been instructed to only speak Dutch - something which is commonplace in gemeentes where the NVA is involved in the governance. Unless you are an EU citizen you will have to attend integration classes including ones to teach you Dutch to at least A2 standard (and you will be tested).
So, yes, Huldenberg will be open to expat movement - providing you speak Dutch.
Communes in Wallonia are much more pragmatic concerning language issues although, obviously, all written communication there will be in French.

Becasse, I am pretty sure it is Flemish policy in general. it has little to do with the N-VA, who only really broke through at the municipal level for the first time in 2012. As for Wallonia, it might theoretically be more pragmatic, but good luck finding someone at the commune who speaks passable English (or Dutch).

Huldenberg is right next to Wavre, I assume that's why she's looking at moving there. That said, I agree with everyone else who has posted so far. If you're going to be sending your children to a French-speaking school, I would simply move to a francophone municipality.
Conversely, if you really want Huldenberg (which certainly is nice and green), why not consider a local Dutch-speaking school? I would be as consistent as possible.

Please ignore J and Becasse they don’t live this way as far as I know and often are negative.
Huldenburgh is a nice quiet commune, it’s easy to get to and from Wavre via the roads depending where you live within the area. Public transport goes from the center of the village to Leuven and also Brussels, I do not think to Wavre though without a change of bus, however as it’s bus so a bit slow to get into town Bxl that is. However it’s not so far to drive to say la hulpe for the train or Tervuren for the tram into brussels..
If your children don’t go to schoool locally you can still find other activities like sports or music locally. The local school system often has a half day Wednesday and many children take clubs or classes then depending on their interests.
Are you think one of the English and French speaking schools in Wavre if so you will meet other parents via school.
I don’t know how old your children are but I’d recommend the BCT as a way to meet other young families who are English speaking if you need that especially they are younger age rang. if not maybe a sport maybe there is plenty of choice. . I’m living pretty close by in Terlanen and if you want to be out of the hustle and bustle of town I’d recommend this area. Tons of good waking, good bike rides many of dedicated bike paths and beautiful countryside here. However negative are depending where you or your significant other work accessing the RO can be very slow in a morning but there are cross country routes that make it faster. Shopping there is one major supermarket in Huldenburgh and a weekly market but that is pricey. A short drive to Overijse offers more choice for shopping for say clothes or shoes and different grocery shops. As far as I’m aware refuse is via wheelie bin and you are charged by the weight of you rubbish. Good luck with the move, there are expats in this area and please ignore the negative from people who just like to moan

Side note to Becasse I would say you are wrong about the commune in my experience from what I am told Overijse is the worst one and even there if you try and speak Dutch they are not unreasonable or rude to you. I’ve heard much worse stories about say Ixelle from Frenche speakingfriends who live there.
Language classes are available for Flemish in all these commune too so people can easily get by and the local Flemish as a rule are much more polite than the francophones in my experience.

Ps Parma are you aware your email is showing I would change your user name if I were you all the best

There are no English speaking schools in Wavre. The level of ignorance is astonishing.