I don't know how good of an idea that would be seeing as how crickets (well pretty much any feeder can do this) have been known to harass and nibble geckos when left with them unattended. I would be more concerned with figuring out why your leo is having troubles finding his feeders or eating before modifying my feeding program. Maybe your leo is the type (like mine) that prefers being hand fed rather than bowl fed. What's going on?
The problem is that they are still juvenies and have a big vivarium for them selves. With mealworms I have no issues because I leave the bowl and when the like they will eat. But when I left crickets the crickets hid under plastic plants and geckos did not find them. I left them for about 2 days.
So I thought of putting them in the hide box.
have you considered a seperate feed box for when you plan on feeding crickets? Or you could put the crickets minus their jumping legs in a tupperware dish in the viv that the leos can get into (maybe with the assistance of a step like a rock) and the crix can't get out of?
Since they're juvies I would first try using a feeding dish in the viv like a long-ish rather than tall-ish tupperware dish that the crix can't get out of since constantly moving juvie leos could stress them and cause them not to want to eat just from the move to a feeding tub. build up something that the leo can access the dish from the outside of it if he wants to crawl in it make sure it's large enough to accomodate his size plus the feeders. If all that is too difficult to do then the other option of a seperate feeding tub is always available for you. I would make sure the juvies are good and hungry the first tie you try a seperte feeding tub just to make sure that they're in the best possible position to want to eat and would be more likely to forget that they're in a strange environment. Maybe take the tub you'd use as a seperate feeding tub and put the leo in there a couple times with out food just so it starts to smell like the leo and could be less stressful overall. Make sure you take the jumper legs off the crix before using either method imo as it will make it easier for the leo to catch them.
You just pull them off with tweezers or your fingers. I really don't think the jumper legs hold that much nutritional value so it won't hurt him to not have them.
You could also use a shallow tupperware dish like those gladware disposeable dishes. They're pretty inexpensive. Might be better than cutting a plastic cup as it could leave a sharp edge that could hurt your leo's sensitive skin.
I do the same thing with my crix I just hold the cricket and rip the big legs off. Bonnie when she is as gravid as she is has a tough time chasing down the crickets but with the legs off she can get them.