Calculating the force may prove very difficult because collision forces change rapidly with time. Theoretically, if you monitored the angular acceleration of the pendulum you might be able to calculate the contact force, however in practice I doubt you would be able to make enough measurements per second to see such a short collision. If you would like to do the pendulum, you may be more successful correlating the impact energy instead of force.
If you would still like to do the force study, you may have more luck with springs. You could mount a spike (or marble) on a compression spring and use a vice to push the egg into the spring. By measuring the compression of the spring you would be able to calculate the force (Provided you know the spring constant of the spring in question).
Also, you may want to consider the non uniformity of the eggs. Some eggs simply have different shapes, shell thicknesses and brittleness which if not controlled could cause problems with your results.