Around that time it should be quieter. You'll find there'll be people who'll have finished their uni year/the early part of year 11s who will be finishing their GCSEs. But I think you'll be okay, I recommend Dark Forest first as this is area is usually quieter then either making your way to Forbidden Valley or X Sector. Leaving Wicker Man til a bit later for crowds to die down (and for it to warm up
ROYJESS has a good idea in starting in different areas each morning as a different option. The only rides that open from 11 are Duel, Runaway Mine Train and the Congo River Rapids.
Hope this helps and if you want any more advice please do ask