Hi!
Please be aware that the need to drink is the second biggest need after breathing. It comes even before the need to eat. This means that healthy, eating piggies with access to fresh, cool water at all times won't be in any danger of dehydration. How much piggies drink individually, varies very widely.
Please make sure that you do not overfeed on veg. The main food of guinea pigs, which should make around 80% of the food intake is grass hay, more hay and then topping it up again plus fresh dog pee free grass (carefully introduced to avoid tummy upsets). Veg basically replaces the wild forage which with guinea pigs used to supplement their grass fibre based diet (it makes only about 15%), so please try to keep it green and leafy. Both the crucial grinding back teeth and the digestion, which takes two runs through the gut to break down the nutritious but tough grass fibres are engineered to cope with it optimally. A hay (and not veg based) diet with only 1 tablespoon of pellets per piggies per day can make a huge difference in long term overall health and add 1-2 years to an average life span, taking it from the bottom end to the upper or even beyond.
Compared with a human diet, grass hays and fresh grass make breakfast, lunch and dinner. Fresh veg and herbs are the equivalent of an afternoon snack and pellets (which have much more fillers than fibre) should make just a dessert.
Please take the time to have a read of our comprehensive diet guide, which looks at diet as a whole but at each possible food group in practical and precise detail. Apart from providing plenty of space, exercise and enrichment (which doesn't have to cost much), a good hay based diet is the best thing ever you can do for your piggies in combination with a weekly weigh-in and body check to help notice developing problems early on when they can still be sorted more cheaply by a vet. Saving up for vet cost as part of their weekly/monthly living cost is the other crucial thing you need to do; illness and emergencies never happen at a convenient time but you do not want to lose a piggy because you haven't done your bit.
Please take the time to read the information - it can really make a difference!
Long Term Balanced General And Special Needs Guinea Pig Diets
Weight - Monitoring and Management
Guinea pig body quirks - What is normal and what not?
A guide to vets fees, insurance and payment support.
How Soon Should My Guinea Pig See A Vet? - A Quick Guide
Here is our much more comprehensive practical step-by-step New Owners information collection, which you will hopefully find both helpful and interesting. We have included things like a course in 'piggy whispering' to make friends with your new piggies more quickly and how to understand key interactive social behaviours together with lots of other very useful stuff. You may want to bookmark, browse, read and re-read the link at need:
Getting Started - New Owners' Most Helpful Guides