Are the vibrational modes of CO2 active at room temperature?
Yes, the vibrational modes are present at any temperature, including absolute zero where the lowest vibrational energy levels only are populated; the zero-point levels. The molecule is linear ( OCO ) so it has $3N-5=4$ vibrational modes for $N=3$ atoms. The symmetric stretch  corresponds to both CO bonds stretching in phase, and asymmetric stretch to one CO stretching while the other compresses (this has highest frequency), and there are two degenerate bends where the OCO angle changes (lowest frequency). If the z-axis is along the OCO bonds, bends are in the zx and in the zy planes. Wikipedia has lots of diagrams showing these vibrational normal modes.

I have calculated the heat capacity as shown in the figure. The translational value is 3R/2 at all but the lowest temperatures (a few K) and similarly for rotational levels, which have a value of R, again above about 50 Kelvin. (The rotational constant is 0.3902 wavenumbers). The vibrational heat capacity from the modes (1388, 667,667, and 2349 wavenumbers) gives the rising curve on the figure. At 300 K the value is about 3.4 R or 28 J/mol/K. It is clear that only a few vibrational quanta are populated at room temperature. The high temperature value of the heat capacity adds another 4R (each vibration counts R) and is not reached until about 4000 K. Clearly never obtained in practice.



Total heat capacity for CO2 vs temperature. The blue line is the total heat capacity, the lower horizontal line has a value R, the upper one R+3R/2. The top horizontal line has no particular importance and is the value at 300 K and is approximately 3.4R as mentioned in the comments.