Hey!
Oh my, no 4 boys wouldn't be much help would they? That's what we're here for!
The size is lovely! Just like I thought... and colour is one of those things that is really in the eye of the beholder when it comes to saturation on yellow diamonds! But honestly? I would wait to have one brought in if I had to and go for a more saturated colour, either a FI or FV (don't worry it WON'T look "orangey" when it comes from Tiffany's!). To me it looks like it's almost washing out. Even within each colour category there is some variance... you might have a really light FY there. And it sounds like you're wishing it had come out a bit more sunny... I think you should be 100% happy with your purchase and return it until they find one you LOVE.
I'm pretty sure (after extensive research!) that the ones on the website are fancy vivid colour (by the way they don't post the ACTUAL picture of the one you're buying under "sola" - I've noticed that! They have a stock picture which doesn't reflect the colour/size very well)... which is why they look more "sunny" than yours ... for reference, mine is fancy vivid (fancy yellow is the lightest, fancy intense the middle, fancy vivid the most saturated) and as yellow and sunny as it is I would have mistaken it for FI - could barely tell the two apart side by side. I was looking for FI but in comparing 4-5 pear pendants, ended up loving the whole look (shape of the pear/colour/size/value) of the FV the most out of four she brought in so that's how I ended up with mine! But I think FI is just fine and really nicely saturated.
The thing is - if you found another .39-ish size and upgraded to FI you really wouldn't end up paying THAT much more - MAYBE $400? That's just a guess based on the ones I was comparing but it won't be that much more to get one you'll be REALLY happy with!