To tell them their baby name options aren’t great?

I assume you don't get out much if you're shocked by the perfectly commonplace name Gigi.

Oh dear god

Like many posters on here you appear to be having difficulty distinguishing between objective fact and subjective opinion. To clarify, what you actually mean is that you personally dislike those names and think they are awful, which is purely a subjective stance, not a statement of fact. Hope that helps.
OP, there is nothing objectively wrong with those names. I would always advise any prospective parent not to reveal their baby name to anyone, even close family, until the baby is here and the name is a fait accompli, otherwise people will, sometimes well-meaningly, try to talk you out of a name you love. There is no name which everyone will like. Some people take a strong dislike to names for a whole host of, often arbitrary, reasons, including having known someone with that name who they didn't like. These purely personal reactions are irrelevant to what someone else wishes to name their precious baby.
I would keep quiet, this would be my advice to anyone considering commenting negatively on someone else's baby choices. you will end up loving the name, whatever they choose, because it will be the name of your wonderful grandchild.

I like Bunny. I like Bunty even more 🤷🏻‍♀️ Gigi…awful.

That’s why everyone gets to name their own child and everyone else (including Grandmothers) should just smile and nod.

Are you sure they are the actual choices? We got so fed up with everyone and his goat wanting to express their views on what our child should be called and which family member on which side should be the middle name, we started going with star wars names like Han and Darth and stuck with it for 4.5 months 🤣

Especially when it won't be unusual for her friends to be called the likes of Dolly, Bambi & Pixie.

A friend of mine - thankfully - called her baby Gigi. I say thankfully because her alternative was Bunny 😱

I knew a woman called Pebble. She was a very successful teacher on the SLT at her school. I really don’t think being called Gigi will hold you back in your career, come on.

She isn't OP's child. She doesn't get a say in the child's name so no, it's none of her business.

They have already very, very clearly told her 'absolutely not' when asked if they will be nicknames. Saying any more won't go down well.

They sound like the names of hair products to me, so no, not great OP.

Ah they’re not so bad. At least they’re names and not fruits or a sequence of numbers.

I don't know why people say it's none of your business. Of course it's your business, it's your grandchild so you will be calling her one of these names if they do use one of them. Wasn't there a thread on here about a grandmother who never called her grandchild by their name?
Completely different if it's a stranger, you may not like the name but it wouldn't affect you, so yes none of your business.

I'd just suggest they have a formal name on the birth certificate and use Gigi/Tiggi day to day, frame it as giving your granddaughter the choice because no-one knows, until 10, 15, 20 years down the line if she wants to blend in with a more mainstream name or stand out with a more unusual name.

The Gigi I knew was Ghislaine. Not ‘that one’ but that would be a good reason to dissuade……

I think Tiggì sounds Nordic

Come on, tell us your birth name! I'm intrigued

the worst naming practice is naming your children one thing but calling them something else. If they are going to use a short name in practice, that is what they should put on the birth certificate

100% this.

unless asked directly I wouldn’t share your opinion on this. They probably already know you’re not thrilled by it by your reaction (unless you’re a good actress) which is fine. You don’t have to love it but you don’t have to share that you don’t love it. And when the baby is here it will be your gorgeous dgc and you wont care what their name is as long as they’re happy and healthy.

Having your first child is an exciting time but also a vulnerable one. Your daughter in law will learn soon enough that everyone has an opinion on everything she does and it’s hard to feel like you’re getting anything right. Respectfully you’ve had your children and made your choices, let them do the same. Parents and parents in law unless asked specifically otherwise are supporting characters, not main characters when it comes to dgc.

There’s no guarantee they will use either of those names when baby is here.

My MIL decided to tell me my dc was “horrible” on their first visit to meet them at the hospital when they were about 6hrs old. It took me about 6 months to not be livid about it lol

Can't imagine how anyone thinks such silly noises are acceptable "names" for anything other than a budgie or a tortoise.

But if they can't see that, no amount of persuasion is likely to help.

Excellent and very well made point.

Hardly a leap from geegee to gee gee is it?

Absolutely, definitely say nothing. Their child, their choice. You had the opportunity to name your children , give them theirs now.
They wont thank you and it wont alter their opinion .
I like Gigi and it is becoming more popular. I always think of tabby cats and uber posh people trying to sound cool when I hear the name Tiggy but it's their choice and won’t effect the child’s life in any significant way.

Mine was Clothilde!

I hated learning French but I still like that name.

Ada is the usual spelling of the name in the UK. Check out Ada Lovelace (or Ada Shelby 😊).

When I was learning French at school many years ago, we were all given French names on day one. Mine was Gigi, which I loathed at first but grew to love. There are much worse names. Tiggy’s one of them, imho, but you’d get used to it. And of course the main thing is, it’s not your child, so yes, you’d definitely be well advised to bite your tongue.

I agree that the names are pretty awful but that no good at all would come of you saying anything. I'm sorry! You'll get used to the name. When you say they don't want a longer one, does that include middle names?

Tiggy Legge Bourke’s name is Alexandra.

AI overview doesn’t know why she’s known as Tiggy but it sounds like a boarding school nickname to me and may not have a real reason behind it.