They will probably stay quite happy in there for a while but it would only be a matter of time I'm afraid until something happened and its not worth the risk. I'm not 100% sure about the female, someone else may be able to help you out there.
The male will probably end up chasing the female before he actually attacks her. Don't get me wrong, they might all be ok but it really isn't worth the risk.
I had my first male in a big tank with 3 females, unfortunately I lost mine to disease, but when I posted a thread on here keeping male and female together was a big no-no. I have since done some research and found that people were right.
Unfortunately, fish stores sometimes don't give the best advice as we have learnt. Keep posting and asking on this forum and people are more than happy to give advice.
If you can't keep your male Betta in a seperate tank see if your lfs will take him back.