I totally understand your concern with your gliders and having someone else care for them. But don't worry too much.
I would put their cage in a glider proof room (if not already), that way if one happens to get out with the sitter, they'll be easier to catch, etc. Even if it's the bathroom.
If you're going to be gone for 6-7 days, you definitely need a sitter. For water, you could just use a water bottle? My guys have a tiny one, and it still can take them over a week to get through all the water.
We freeze a lot of our fruits for our gliders since it's way easier to extend fruit that way. We pop out an ice cube of fruit, and ice cube of veggies, and place them in their metal dish. Then we take a second lager bowl, fill it with hot water, and place the metal bowl in that. It helps them dethaw much faster. Alternatively you can just put the ice cubes in a microwavable bowl, and microwave them. Esp since it'll be easier for the sitter, and will just be a few days. Then we add fresh protien and calcium powder. You could also pre mix all of these things (fruit, veggies, protein, powders) into separate baggies, and portion out the seven days that way.
Just plan evyerthing out by amount for their meals, and then walk your sitter through everything. Even label the food in bags "day 1, day 2, day 3.." that way it's stress free for the sitter. And you can make separate meals with protein etc, all ready. Leave a printed piece of paper with each instruction. "Step one-defrost two ice cubes (or bag). Step two-add in calcium/protien/whatever (if not added yet). Step three-feed at this time...etc"
It might be easier for your sitter to come earlier in the day? Food would be less fresh, but then you're gliders will definitely be asleep.
But I think the best peace of mind with be having the gliders in a room that the sitter can close the door behind them (tell them to do this) and can feed them. Show the sitter how to catch them with a piece of fleece, or with pouch if they escape. And this way they'll be more confident if anything happens, and you'll have the peace of mind, knowing if one got out that it'll be ok.
In your walk through with the sitter just make sure you stress to always have the door closed when opening the cage doors. Explain how quickly they can get out. And run through things like toilet seat down, etc.
Hope this helps <3