This would be my recommendation. I took someone there who was a bit geeky and they absolutely loved it having not spent much time in London before.
It is admittedly just a shop but the merchandise they have there is phenomenal.
Upstairs (ground) they have a massive section of merchandise with things like the portal guns and replica swords and such like. Massive sections on dr who and stuff as well. Downstairs they have an incredible 'book store' kind of section.
It's not the closest thing to the shard, but personally I'd go there, and then you have an array or places around covent garden for food:
Food at borough market could be good, but it depends what you're into. American style burgers are all the rage right now and I think shake shack, and five guys both have places in covent garden. I haven't been to shake shack but have heard good things. Five guys was just as good as anywhere else but their drinks selection (soft, not alcoholic) blew me away. I think meat market(?) can't quite remember the name of that one (look up meat liquor and find the sister restaurants) is also in covent garden. The meat X restaurants vary in my mind for burger quality between establishments. That said their sides are always very good (have monkey fingers if you're ok with a bit of spice) and the alcohol selection is also very very good (grog and Their other drink that you can only have two of are amazing) but highly alcoholic (hence limits on how many you can have).
The other options would be Byron, breakfast club or patty and bun but the latter two have massive queues frequently and I don't think they have places in CG.
All of the above are actually reasonably well priced for London as well. Search for any on google and you'll find the menus. Alcohol tends to be where you get charged a decent amount . Expect to pay about £8 for a strong cocktail.
Oh, and if you're looking for something sweet then I'd go to laduree. It's extortionate but the macaroons are absolutely astonishing. Best I've ever had (providing you like macaroons)
kd