I think this challenge is easy for veteran KSP players, but I have made my first successful 4.65 ton rocket which can head to the Mun and then Ike in one launch. Except I forgot a parachute so I couldn't return home (I had to fuel to do so).
I think I could bring the weight down to just 3 tons if I removed some solar panels, excess weight and used a smaller battery.
Here's the video:
Enjoy! And thanks for viewing!