I taught my son seven (and a few randoms) languages to varying degrees simultaneously ....
Personally if I had been able to get LR Mandarin at the same time as LR English I would have.
It also depends on why you want to teach the multiple languages. For me it wasn't about teaching him to be multi-lingual as a baby. We weren't actually attempting to teach him the languages I ... had read the lines in his book stating that they lose the sounds they don't hear in their everyday life. Hence the decision to get so many languages underway it was actually an attempt to build the pathways for later - little did I know he would learn them.
TmS,
Do you speak all the 7 languages you decided to teach your son? How old was him when you start teaching him?
My idea on teaching my grandsons language is exactly the same as you express. I want them to have the foundations so that if later in life they want to continue with any of the languages, it will be easier having been expose to the differente sounds. with english and maybe french yes i would like them to be multilingual. Normally all kids in my country (middle class) go to bilingual private schools and learn one foreing language (mostly english). Even public schools are teaching english.
I think i will follow your suggestion but maybe starting Chinese 1 month behind.
Thanks a lot for your comments.