Jenny,
Now that you have established rules with your potential lover, establish rules with your husband. What does he want you to do. What does he not want you to do. What do you want him to do and what does he not want to do. As you said, just because your husband likes something in fantasy does not mean he will like it in real life. Take for example snowballing your lover's cum to your husband, this may be a huge turn on in fantasy but may be very overwhelming in reality (e.g. think of the first time you gave a blowjob.) You should also consider a STOP word. A word that if said by anyone would stop everything. The stop word should be something that would be out of the ordinary in the setting like yelling out "string bean".
In any event start slow and watch for your husband's reaction. Start with kissing and move to a handjob. If his body language tells you he is uneasy stop. If on the other hand he starts masturbating then move along to giving your lover a blowjob, but always be mindful of your husband's body language.
Now that you have established rules with your potential lover, establish rules with your husband. What does he want you to do. What does he not want you to do. What do you want him to do and what does he not want to do. As you said, just because your husband likes something in fantasy does not mean he will like it in real life. Take for example snowballing your lover's cum to your husband, this may be a huge turn on in fantasy but may be very overwhelming in reality (e.g. think of the first time you gave a blowjob.) You should also consider a STOP word. A word that if said by anyone would stop everything. The stop word should be something that would be out of the ordinary in the setting like yelling out "string bean".
In any event start slow and watch for your husband's reaction. Start with kissing and move to a handjob. If his body language tells you he is uneasy stop. If on the other hand he starts masturbating then move along to giving your lover a blowjob, but always be mindful of your husband's body language.