Mixing sperm for a surrogate

Gay couples who want to have a child via surrogacy have various options to choose from in IVF surrogacy:

1. Creating embryos using the sperm of one of them. The identity of the father that has a genetic link to the child is known.
2. Creating embryos using the sperm of both of them. Two embryos will be transferred to the surrogate.
3. Mixing sperm and selecting one embryo at random. The identity of the biological father will remain unknown unless a DNA test were done.