My ex-girlfriend wants to give up her rights to our two children. Can we do that without a lawyer? In Iowa? I have married and can provide a stable home for them. They are with me 95% of the time now.

Not really, it has to be done though the courts and for your protection you want it done correctly.

1. she can't just give up her rights unless your new wife wants to adopt them.

2. if you are going to have new wife adopt, it is very complicated and you need an attorney

3. if not going to adopt, you have to file in court for custody and get a court order giving you custody. The ex does not have to file for anything, and thus you get child full time.

Only a court can terminate parental rights. So you have to go through Family Court. The court will generally not issue a TPR unless your new wife is ready to adopt. To prepare a petition for adoption, you should go through a Family Law attorney.