Supramolecular assemblies of dendrimers, with defined structures and tunable functionalities, are promising functional materials. Here we report a ternary system (lanthanide ion/bis-ligand/PAMAM dendrimer) capable of assembling in a cooperative way by forming a complex between anionic (metal-ligand) coordination polymers and the cationic PAMAM dendrimers. In off-stoichiometric mixtures, charge-stabilized spherical nanoparticles of similar to 100 nm appear; they have either negative or positive surface charges depending on what the excess component is. Introducing different trivalent lanthanide ions, Ln(III), in the coordination allows tuning both the luminescence emission spectrum and the magnetic relaxivity without affecting the assembly process or the final structure of the particles; this makes them interesting in the context of application. Moreover, the incorporated dendrimer allows us to add functional nanocargo, for example, Au nanoparticles in the cavities of these molecules, again without disturbing the assembly. In this novel way, we obtain versatile, multilevel hierarchical supramolecular dendrimer-containing assemblies with good control over their structures and functionalities. This is very difficult to achieve with conventional covalent compounds but becomes possible because of the supramolecular nature of the coordination polymers and the strong cooperative assembly.