It should be okay to run Sims 3, but you will likely get pretty poor performance in Sims 4. I recommend you add another stick of 4GB RAM though for three reasons:
#1 - Better graphics performance. Two sticks of RAM means it will run at full speed (dual channel) rather than half speed (single channel). That can improve integrated graphics performance by around 5% to 15%, but it depends on the specific game.
#2 - Windows has more resources, there will be less disk caching when Windows starts running out of physical memory and play games can use up a lot of memory. Disk caching is swapping data between the RAM and hard drive which can slow down performance.
#3 - This is related to #2. Not enough RAM can cause Sims 3 to crash or the laptop to simply freeze which can cost you hours of game time especially if you do not save very often. I have a friend who used to play the Sims 3 a lot and she complained about periodic crashing and freezing. After upgrading the RAM from 4GB to 8GB those problems became a lot less frequent.