was in Charyn canyon a few days ago. Entrance fee for cyclist was 752 KZT. This is valid for several days + nights ; 3 of us actually spent 2 nights in the canyon.
The water of the river is suitable for drinking after purification (filter or boil or UV or pills). I did not try to drink it as is. A guy sells bottles of fresh mineral water, and a limited quantity of tea or bier, on the parking 400m below the entrance of the park (ranger's house + cashier) ; Ihe seems to be there almost every afternoon.
The beautiful "road" which goes to the "Eko Park" site (so called valley of castles - dolina zamokov) has a short very steep section at the beginning when going down. Depending on the bike, its load and the cyclist, it may be necessary to carry/push panniers and bike separately when coming back uphill. The rest is not steep but often sandy, so there are sections where we have to push the bike, but overall it is a bit shorter than to walk.
No shop in the Eko Park, but a kafe (drinks + basic restaurant) and a few yurts or bungalows for rent (bungalow 8000 KZT for 2 beds, yurts 40000 KZT for 8 persons) and places for a few tents near the river. Banks and tables with shade.
Possible -and very pleasant when it's hot- to swim in the Charyn river, but take care of the stream ! Better to stay on the left bank near the mini-beach, a spot where water is quieter.
NOTE: there are a couple of possible camp spots along Charyn river, about 20 km upstream from the park. It is when the road between Kökpek and Aksay crosses the river. Less than 1 km before and after the bridge, there are gravel roads to the river. It is free, not always very clean, and kazakh army sometimes closes the "road" to the right bank (south of the bridge) because of military fire drills