Radium produces the most radiation by miles. The plutonium gives off some alpha radiation that won’t hurt you if you don’t eat it. (Eye protection would be a good idea I suppose.) I don’t remember what U-235 emits but I don’t think it’s a huge amount.
The half-life of 235U is hundreds of millions of years so it is not a concern. However, it will literally become a nuke if too much (a few liters or 60 kg) get too close together.
The half-life of plutonium-239 is tens of thousands of years so only a thousandth will get a chance to hurt Theodore over his lifetime. However, it is probably chemically toxic so it might cause non-radiation poisoning.
Radium-225 will decay in days, and will quickly go through 7 more radioactive reactions, both alpha and beta, before becoming essentially stable bismuth. It is the worst by far.
