S.H.
Yes, you can do it.
I speak English to my kids only. My Husband speaks French, only. Grandma speaks Japanese and English to them.
My kids know ALL languages. They are now 3 and 7 years old. They are FLUENT in all languages. NOW, at their ages.
We taught our kids multi-languages because we are multi-cultural and it is good for kids to learn other languages and cultures.
Kids are sponges... they can and do learn MULTI-languages. In Europe, many people speak even 5 languages just fine.
BUT... You CANNOT except that their "spoken" language and reading ability in those languages... to occur at the SAME time. Children's cognitive AND "language" development occurs in STAGES and PER their age.... as their brain develops. So keep that in mind. At this age, the brain is not even FULLY developed nor its synapses and connections. The brain for that matter, is not even "fully" developed until you are in your 20's.
Now, the fact that your BABY says "Ball" is good. AND She probably cognitively understands the word "ball" in ALL the other languages too.... but she is speaking it in English. At this time. That is fine. When she gets older and develops more, she WILL say it in other languages. Just do NOT rush it. Trust in that.
My kids, even before 1 years old, understood EVERYTHING that was told to them in other languages. Completely. Then, once they started to "talk" they talked in English. THEN, when they got older (about 2-3 years old), they started to speak in ALL the languages, gradually... ON THEIR OWN, per their development and age AND ability. They are completely Fluent in all. We did not pressure them.
The thing is... don't make it something irritating for the kid or that they have to "study" for it or "learn" it or be tested on it. It is everyday normal life and they are just, through exposure, absorbing all the different languages. NATURALLY. Like many many many kids and people do.
It has to be natural learning. A child WILL understand... and you will not confuse them. It is the way they grow up.
BUT, if I were you, I would speak to your child in only ONE language. YOUR main language. The caution here is that: if her parents (You and Hubby) speaks to her using multi-languages within 1 sentence all the time... then the child may learn an improper way of talking/sentence structure etc. She will learn THAT way of "talking" because you/everyone is talking to her in spliced sentences.
And NO... multi-languages does not "cause" a speech "delay." Meaning, it does NOT cause a child "NOT" to be able to talk.... nor to understand. The child may merely be "organizing" everything in their heads. So do not assume that all multi-lingual children automatically will have a speech delay and that it is bad and something is "wrong."
Einstein did not talk until 3 years old.
The other relatives, will just have to wait AND understand that... until your daughter is old enough AND mature enough to speak in all languages. It will take time and most of her formative years. And until then, you WILL have to translate for her AND them. But do NOT pressure her. My kids, HATE being 'nagged' to speak in other languages by their other relatives or being "tested" on what they know, or being told "Say something in french,japanese,english etc." Or that it is a competition to see how 'smart' they are or that one language is 'better' than the other.
The main thing being: you NEED to allow the child to learn at their own pace, naturally, and to grow INTO it... per their age and maturity and developmental based stages.
AND, you cannot control what kind of "accent" the child will have... when speaking all the languages. Not even adults have perfect accents. It is attained, in time. Even within America or Europe, there are different "accents" or dialects. So there is no single "accent" that is the proper accent. It depends on where you grew up in or are exposed to most of the time. Even linguists... don't have "perfect" accents in ALL languages.
A child, will be forming their language "ability" all their lives, whether it be in 1 language or multi-languages. And they will have their own preferences too.
For example: my friends, have multi-language kids too... and she has 3 kids. BUT, one of the kids went through a "phase" where he would ONLY speak 1 of the languages... even though he was capable of speaking/understanding the other languages. It was a phase. And you have to allow for that too. Its just growing up.
All the best,
Susan