squarespace or free font similar to optima

Hi -- I'm building a website for my children's book (to be released soon). The book uses Optima (mostly Pro Roman) as its main font, with some accent fonts (eg Adorn Pro Roman) used elsewhere.

I'm a bootstrapping website developer and a first time author -- I don't want to pay a yearly fee (at this point, anyway) for a web license for Optima. Can anyone recommend a font, either native to Squarespace or free for import, that has a similar look and feel? The options are overwhelming for a newbie, and I know that professional designers know their fonts inside and out.

Thanks!

Carol