Honour Middle Name

I'm days away from my due date and my husband and I don't know what we're having. If it's a girl, our top name choice is Sophie, but all we know for sure is that we want her middle name to honour my husband's late mother.

What we're playing around with right now is whether to use her proper name vs. the one she always wished she'd had (and would sometimes introduce herself as to strangers). While not the exact name, a really close example is Helen as his mother's name, and Helena as the name she preferred.

As an additional consideration, our mothers share the same name (both "Helen").

So my question is. If it were you, would you use Helen or Helena? Do you think it would be strange to use an honour name that was not actually the name of the person being honoured? I'm thinking it could be a good way to distinguish who the "honour" is for between my mom and his... But don't know if the true meaning gets lost by changing it.

Thoughts??