You can start jumping at any age, we have a couple who ski with us who are both over 50 and just learnt to jump, absolutely love it. You need to make sure you have the right instruction and planning before hand to make it really fun. Just being thrown over the ramp is definitely not a good plan.
Get to know your skis first and foremost, we don't let people go over until they can cut both direction, jump the wakes without pulling on the handle, cross the wakes by lifting one ski up and cutting through on one ski. We need to see you be balanced and in control of the jump skis before sliding over.
When going over for the first time we always use a rope release just in case someone falls into the handle.
Basically drive 18-20mph close to the ramp, head up, arms straight, skis shoulder width apart and freeze.
Lastly don't use long skis for your first time, try to use skis shorter than 80", preferably a pair of old 74" is best.
If you go over enjoy, its a lot of fun.
Thomas Asher