The party is for your child who is turning 3.
So I assume, your daughter's friends will be invited or her friends from Preschool. HER age, friends. It is for a 3 year old Birthday party. HER birthday. So you need to keep that in mind.
DID your daughter, SAY who she wants to invite????? It is her party.
How old is the older kids?
Sure, have them be helpers, if that keeps the older kids from taking over the party. But speak to the Mom about it.
But keep the focus on your daughter, it is HER birthday.
You don't have to invite the older siblings.
I have seen and gotten invitations that would state "Sally and 1 parent is invited to Erica's 3rd Birthday party."
Or you only invite guests that are your daughter's peers. HER group of friends.
As long as the other kids, know that this is your daughter's party, and not theirs, hopefully they will have manners about it. Or that their parents, keeps them in line... so that they do not take-over, the party. That would be RUDE guests and kids.
When I have had B-day parties for my kids... (and their friends have siblings), the Mom themselves, only brought the child that was invited. AND if they did bring the other siblings, they always asked me first if it was okay. BUT the Mom, always made a point, of telling their other kids that "This is Erica's birthday party....and your sister was invited..." And they did not expect... to be the focus. They were polite about it all.