How would I buffer an IPoint to do an intersection check using IRelationalOperator?

I have, for arguments sake:

IPoint p1 = xxx;
IPoint p2 = yyy;
IRelationalOperator rel1 = (IRelationalOperator)p1;
   if (rel.Intersects (p2))
    // Do something

But now I want to add a tolerance to my check, so I assume the right way to do that is by either buffering p1 or p2. Right? How do I add such a buffer?

Note: the Intersects method I am using is an extension method I wrote to simplify my code. Here it is:

/// <summary>
/// Returns true if the IGeometry is intersected.
/// This method negates the Disjoint method.
/// </summary>
/// <param name="relOp">The rel op.</param>
/// <param name="other">The other.</param>
/// <returns></returns>
public static bool Intersects (
    this IRelationalOperator relOp,
    IGeometry other)
{
    return (!relOp.Disjoint (other));
}