Guineas are skittish by nature, that's just how they are hardwired and it usually takes them a long long time to feel comfortable enough to come close enough to me to get a treat or take them from my hand. Some of my birds will eat out of my hand without a second thought, or the feed scoop/bucket that I am holding, but not all of them will... it mainly depends how hungry they are and if there is still food in their feeder when I offer them treats, lol. Getting them to this point takes some major time and patience time tho, they don't just automatically trust that what I have for them is worth the risk of them possibly being touched or heaven forbid, caught.... (except if I have been brooding them with a few Turkey Poults, who are naturally little piggies and MUCH tamer so the keets quickly learn to ignore my hands and come running to grab the worms before the big piggy Turkeys get them all). But this method below, for just a batch of keets has worked pretty well for me, many times...
Once I am in the pen with them and they have calmed down, I move slowly and sprinkling the worms/treats in a metal treat pan, it definitely gets their attention (even if they are just manically piling in the corner and screeching at the time, acting like I am going to eat them, lol). I try to use the same treat dish each time and I'll also repeat the same call over and over each time that I give them treats or food (like a broken record) so they get to know that noise and that particular call means food/treats (If I have hatched the keets myself then I'll actually start using the treat/food call from day one, in the brooder... and this call will be the call that eventually brings them running to me or to the coop when I call them, so stick with the same call if possible). Keets will freak out over anything new, even over a silly harmless pie tin/treat pan or new food dish, so you may want to give them some time to adjust to whatever you plan on using for treats and just offer some treats/feed in that each day, calling to them as you sprinkle the treats in and then walk out and let them investigate on their own comfort terms. I'll keep doing this a few days in a row so they get used to treats being in the pan before I actually decide to stay/sit in the pen with them and work with them. And sometimes at first I have to be completely out of their sight before they will go see what the new scary thing in their pen is. Dorky birds.
After they consistently start eating the treats from the pan I try to spend as much time in the pen with them as I can, (and this is another situation where them being a little hungry can work to your benefit)... I'll let their feeder go empty for a few hours, then go in, get settled, let them calm down and then put some treats or feed in their treat pan, and call their food call to them. Then I'll move back and give them some space to come get the feed/treats, but I'll stay in the pen. I don't ever reach for them or try to pet them, I just stay calm and work on getting them used to me being there and to not be so skittish about coming close to get the yummies. Pretty soon after doing this a few days in a row I can usually move the treat pan a little closer to me, then a little closer the next time etc... they will eventually figure out you aren't so bad after all, AND that you bring them yummies. Eventually the little pigs will want the treats so badly that they will start to eat out of the scoop/bucket before I even get a chance to put it in their treat pan. When they start doing this I just use the bucket and get sneaky, having my hand in the bucket lifting up a handful of feed for them (still in the bucket tho). Some will run off once they realize AHHH it's a HAND!!!, but eventually most of them decide it's ok to eat from my hand hand if there's no other choice for getting treats. Most, not all.
It'll take some time to gain this much of their trust, so don't expect this to happen the first try, or even the 2nd or 3rd... and as hard as it is resist trying to reach out and touch/pet them, because that just causes your progress to backslide. Guineas really do not like being touched or petted, period... but the tamer/calmer they get being around you the more chances you'll have later on to sneak in a few pets here and there, lol. If you have no luck with getting them to calm down enough to eat from your hand or anywhere close to you then at least keep working ion their food/treat call over and over every time you feed them or give them treats. As I mentioned that call will be a great lure to getting them in each night, or even just getting them to come back closer to home if they wander too far. I like to call my birds throughout the day at random times for treats... it keeps them guessing and also keeps them a little closer to home.
Hope that helps, best of luck.