Louvain-La-Neuve is about 30km from the centre of Brussels, it would be a minimum of 30 minutes commute. It is a new town, lots of cycle paths, pedestrian walkways. French is the only official language there.
I would do research of where husband's colleagues live, if the office has many international colleagues, ask around to see if the majority live local or not. I am guessing there are not a whole lot of English speakers in this area, compared to the population you find in French dominated East Brussels and the Flemish (Dutch) speaking communes east of Brussels. It really is a personal choice, if you want to live close to work, in a more "Belgian French" town or if you are prepared to have a commute for a more international population. The housing costs will be considerably less in LLN than in the Brussels area.
Another possibility for location is along the E411 motorway from LLN up to east Brussels - Wavre, Bierges, Limal, Rixensart, Genval all French speaking, or Overijse, Tervuren, Hoeillart which are Dutch speaking. There is a local French school which offers teaching time in English a few hours a week, extra fees apply I think no more than 4k per year, about 40% are native English speakers. It's called Ecole le Verseau. It is unique in Belgium in teaching majority French and a few hours of English. I'd personally live as close as possible to this school, given work in LLN, but in fact a great proportion of children commute from Brussels to go this school. HOWEVER, chances are the school will have no places, so if basing a house on going to this school, secure the school place first before looking for a house. The train line runs through Hoeillart, Genval, Rixensart to LLN, so this is another consideration for commuting options. Most employeurs pay all or most public transportation costs.
A third option I owuld consider is east Brussels area : Watermael-Boitsfort, Auderghem, Woluwe St Pierre, Woluwe St Lambert, just outside and officially in Flanders but French speaking are Wezembeek-Oppem and Kraainem. These areas are very very popular with expats, housing can be very expensive here, a 4 bed can easily cost 2k per month for example.
You will find houses with gardens everywhere, even in central Brussels, so do not worry about that.
Your biggest problem, especially in Brussels, when it comes to schooling is finding a place. Most children are enrolled in school between 6 months and 18 months old. School starts at 2 1/2 and most children start school at this age, so you would be looking for a place when most places are already taken.
If your husband comes under the Belgian tax system, it would be financially better to transfer to Belgian child benefit - it took me 18 months to do this and got a whopping great back-pay. Your husband can claim any child expenses under his tax declaration and pay less tax.
As to your employment paid from the UK, you will still have to declare it to the Belgian Tax authorities, I am guessing you COULD transfer your national insurance contributions to the Belgian system. If you would have paid more being paid by a Belgian company, the Belgian tax system would ask for you to pay additional tax on your UK income.
Finally, you will find nearly every house for rent in Belgium advertised on www.immoweb.be
A good idea is to get to know the post codes of areas very quickly and make great use of google mapping.