In a complicated situation, the first thing to do is to identify the facts that matter. Here's a good start:
1. You want to stack UTG. He's the guy with the big stack. CO's half stack would be nice, too, but should not be your primary target when you flop the nuts.
2. If a jack or an ace falls, you will either be splitting with someone else or will get very little extra value out of the hand.
3. By just calling the flop, your goal presumably is to keep UTG in the pot.
So far so good. Now that we can focus on UTG rather than CO, the question we need to ask ourselves is how we maximize value versus UTG. How does his range change when we call the flop versus raising it?
Any person's range can be divided into a short list of categories:
1. Air. Completely worthless. Only way to get value out of this part of anyone's range is to induce a bluff. E.g. 76s.
2. Weak made hands. Will call small bets, but nothing else. Won't stack off. Will never raise. E.g. Q8s.
3. Decent made hands. E.g. K8s. Will call larger bets. Probably won't stack off unless you convince him that you're bluffing
and he makes a hero call.
4. Strong hands. E.g. two pairs on this board. Will stack off unless the board comes four to a straight.
5. Big hands. Bottom straights and sets.
Normally, I wouldn't separate 4 and 5 into two different groups, but in this hand they matter. The difference is how group 4 compare to group 5 when you raise; strong hands probably just flat (fearing they're up against an even stronger hand) whereas bottom straights and sets are more likely to reraise trying to get it in right away.
What can we say about the other groups?
1 is (almost) never coming along no matter what you do. People don't often try to bluff into multiway pots, especially not on broadway boards. This group is, in other words, not interesting to us.
2 will maybe overcall, but fold if we raise.
3 will definitely overcall, but might fold if we raise.
4 will probably reraise if we call, but just call if we raise.
5 will probably reraise no matter what we do.
And now we learn something useful: The groups we need to target are 3 and 4. Why? Because 1, 2 and 5 don't matter! 2 doesn't matter because we shouldn't be interested in tiny pots when we flop the nuts, and we can't win more. And 5 doesn't matter because we're getting it in regardless of what we do, so we don't have to care.
Normally, the next step in the analysis is to compare relative frequencies of the groups, but we don't have to: it's clear that we get the most value out of both 3 and 4 by just calling.
So we call the flop.
On the turn, you can do a similar analysis, except it's now out of the question that you're up against group 1, and it's unlikely that it's group 4 or 5, so you change your tactics accordingly: Maximize against group 2 and 3, and start eyeing CO's stack instead, because you're unlikely to get at UTG's.
I'll leave the turn decision as an exercise to the reader.