1) buildworld and upgrade to 4.4-STABLE, then cvsup your ports tree.
>> Is it possible to just cvsup the ports without cvsup the core system
Yes but unreliable and not recommended. You need to install /usr/ports/sysutils/portupgrade
>> since I don't want my webserver to go down
Not a good excuse. Further, while building world, all daemons can be up and running like usual. You just need a reboot after buildworld + recompile your kernel and that's the only moment your webserver will go down.
If you consider yourself a FreeBSD user (like telling others, hey I run FreeBSD box and I am proud of myself
), you need this essential step - buildworld. If you haven't tried to buildworld, do not tell anyone that you are running a FreeBSD box, you don't deserve to be a FreeBSD user.
So do it now since you will have to do this sooner or later anyway, if you continue to use FreeBSD.