We were cautioned against Pedialyte at that age per our doctor. He said unless they were clearly dehydrated, the Pedialyte only served to replace vital formula and/or breastmilk.
As for treating the mucus at that age we did two things per our doctor's recommendations. First we elevated the head of the crib with a stack of books under each leg. The idea being you don't want them laying flat. Your congestion gets worse when you lay down and the same is true for babies. For my youngest his congestion was so bad and so long lasting, he actually slept in his bouncer for several weeks. His car seat would have worked but the bouncer allowed him a bit more room to stretch out. We figured if he wasn't scrunched up, it would help the congestion issue more. The key here is upright positioning for sleeping. The more upright, the easier it is for them to breathe and not have the mucus gum up the works.
Second we slathered Maty's All Natural Baby Chest rub (baby Vicks but with more natural ingredients) a) on their feet in and then put on their socks and b) on their chest and back before putting on their pajamas. Our doctor said there is no study to support the slathering of baby Vicks on feet but it certainly won't hurt them. Besides he said every parent feels better doing something for a sick child. :) On their chest it helps loosen mucus because they are inhaling it continuously.
I also highly recommend using the baby saline before trying to suction his nose. Follow the saline directions. But if I remember correctly you want the baby sitting upright, spray in each nostril, let sit a bit and then suction. Be careful with the suction. If you get too aggressive, it will cause nose bleeds and/or swollen nasal tissue which will certainly not help his congestion. We found the nose suctioning job to be best done with two people. I would hold, position, restrain, and calm while my husband could focus on the gentle suctioning job.
Finally during the day try to keep your baby as upright as possible as often as possible so the congestion doesn't settle in his chest/lungs. We did the suction business every morning and every night and as needed during the day. Removing the mucus seemed to really help.
If you use a humidifier, make sure you keep it clean and use it per the instructions. You can create problems with a dirty machine and not using it the way it was intended. Good luck. I hope your baby gets better quickly.