Two racks of quarters will be plenty. But you definitely need to bump up the rest of the denoms a bit too. Two racks of $1s per table will be fine for any stake up to $1/2, so bump those to 400 total at least.
If you're wanting to accommodate deep(ish) $1/2 play, I'm assuming you mean $500 max buy-ins. You'll quickly run up the $5 total if you give that all in $5s (as they would in a casino), but let's assume that everyone should have minimum 40 $5s. Two tables of 10 that's 800 $5s. If you think you'll not have full tables, even two tables of 8 will require 640 $5s.
If you want to be conservative and think you'll typically not have more than 8 players per table and chance running under 40 $5s per player, not a big problem, but you should have absolutely minimum 600 $5s to run two tables of $1/2. That's still below what I'd want, but it will work for two 8-max tables.
Now consider that you'll want people to be able to rebuy at least once each minimum. For 16 players that will mean you'll need $16k total bank. So after your 600 $5s, you'll need to come up with another $13k. $100s and $500s are fine for rebuys, but honestly you don't want those to be workhorse chips even in deep stack $1/2 games, so I'd buy as many $25s as you can to get up to $13k.
You'll need bare minimum enough to cover supplement the $5s for everyone's initial buy-in. So after the 40 $5s ($200), you'll need 12 $25s per player. With 16 players, that's 192 already. So if you buy 200 $1s, 600 $5s, and 200 $25s, you'll be at a total bank of $8,200. To get the rest of the way to the $16k total bank, you'll need 78 $100s. I'd bump that to a full rack. And then you'll have your 5 $500s to cover another 5 buy-ins.
So:
200 quarters
200 $1
600 $5
200 $25
100 $100
I'd still prefer more $5s and $25s, but the above should work for a two table $500 max $1/2 game.
