What was the infected file name (is it the installer or a file within it), what was the virus/trojan name given by avast ?
If you are happy about the use of swpr and you are sure that there is no other risk other than its perceived risk and you accept this risk then you can add it to add it to the exclusions lists Program Settings, Exclusions and the Standard Shield, Customize, Advanced and Program Settings, Exclusions.
That should allow you to install it but you might have further issues after installation so as files are unpacked and installed.
You may need to add it (the detected file/s) to the Exclusions Lists also. You may also have to add the programs executable file to the ignored processes list in the avast4.ini file, but we can look at that after you get it installed.
Instead of using malicious software to monitor things, you better set your security up properly and give others no full access but a limited account with restrictions. There is no need to spy on people.
You have already said you want to use the program so have to decide on the risk, key loggers by there nature can be used for good or evil. avast can’t decide what that might be. You could also check the offending/suspect file at: VirusTotal - Multi engine on-line virus scanner Or Jotti - Multi engine on-line virus scanner if any other scanners here detect them it is less likely to be a false positive. You can’t do this with the file in the chest, you will need to move it out.
If your concern is as a parent keeping an eye on what the kids get up to then I suggest you look at this program that can block content rather than find out afterwards where they have been. Naomi Parental Control software (freeware) http://www.radiance.m6.net/
Naomi works very well and it’s a content filter. It closes the browser connection when p0rn is showed.
Other content filter that works very well is K9 (http://license.k9webprotection.com/download.html)