WSL to St Gilles every day? I certainly wouldn't do that with a young child, I wouldn't even expect a big one to do it. Hellish journey.
5 years means at some point, you'll have to look for a primaire place. The older your child, the harder it is to get a place. Most children start at 2.5 to 3 years, with every year upwards, you are relying on children leaving a school to get a place at your desired school. Most schools are fondamentales or linked maternelles/primaires, very few schools which are stand-alone primaires, so most people choose their primaire at 2.5 to 3 years. In your circumstances, it would not really be a good decision on this point alone to choose Tutti Frutti, especially if your child is already over the age of 3 years old.
You are already too late for many local maternelles in Brussels for next year, so I'd be applying right now for as many as possible and trying to guess where you'd be living. WSL to Etterbeek is an excellent choice, goes from urban to suburban in that area, St Gilles has in my opinion not one single advantage over Etterbeek and WSL for living with children.
If you started November to June in English, you could look at Roots and Wings in WSP, in the middle of Parc Parmentier. It's possible you'll be within walking distance or on a quick tram/bus route to this school. It's English only, which if I were in your shoes with French at home, I'd say it's a far better environment to support English than at 50% English 50% French school. The fees are really not that bad there, you show your income and the owner will probably do you a deal. Then you could review how long you wish to support English, whether to look for a local French school, supporting English with after-school activities instead. If your child has already been 2 or 3 years in English, rest of school year at Roots and Wings, next September in French with after-school in English, that should be more than enough and probably more effective than spending 4 hours of your own day crossing the city, 2 hours of your child's time crossing the city, to a school where maybe less than 50% of the children speak English and where only 50% of the time is in English. 1 hour in exclusive English after-school activities per day will be more effective than 3 hours in a school environment where your child might be a minority of English speakers.
And after all that, the parents I know with children at Tutti Frutti are all quite happy, but none of the kids have come out with much French at all, but all the parents were aware of that at the beginning, it really is a school used mainly by those transitting Belgium or by Eurocrat children whose children will at some point go to European school and spend some of their time in English, for them it's a good choice, for your circumstances, I would be really seriously re-thinking strategy.
