I don't understand your worry. You're making a command decision not to take two pax for W&B reasons. That's perfectly ok and in fact shows good captaincy.
If you're low on hours it's best not to tackle too many "new" things at the same time anyway. Handling passengers takes vital mental capacity away from flying the plane. The more passengers, the more that can go wrong.
And if you're worried about the legal issue: No, as long as you only accept money towards a fair share of the flying costs, there is no issue here. Only if your passengers start to pay more than their fair share, or even the cost of the flight outright, might you be on the wrong side of the thin line.