I don't think you can go wrong with any of these! I will say though that I think of Greta as a nn rather than a given name, but maybe that's just me. I voted Charlotte but I like them all.
LFAF Awards
me: 27 | husband: 35 IR PCOS dx Sept. 2014
married May 2015 --> started NTNP BFP 6.28.15 - EDD 3.6.16 baby #1born 2.19.16
All great names! I would stay away from Eleanor and Charlotte just due to popularity. Greta is adorable! But I think Claire fits best with your sibset.
I voted Claire. Such a sweet, simple name. I love Charlotte too, if the popularity doesn't bother you. I wouldn't use Gretta with your daughters' name. Since their names are pretty common, it feels odd in comparison.
Re: Choose girl name for DD3 Poll
me: 27 | husband: 35
IR PCOS dx Sept. 2014
married May 2015 --> started NTNP
BFP 6.28.15 - EDD 3.6.16
baby #1 born 2.19.16
TTC #2 in April 2017
BFP 12.30.17 - EDD 9.6.18
Fertility Friend Chart
2. Eleanor
3. Claire
4. Charlotte
Love them all but Greta gets the win from me.