there are risks, however provided you are experienced with your kites and buggy and are aware of the dangers of attatching yourself to your kite & buggy, you can minimise these.
Using velcro on the lapbelt is fine as long as it is strong enough.
You will eventually find it foreign to buggy any other way.
Before you start make sure you talk to some of the experienced jumpers & always try and have others around on the beach in case you have difficulties.
It's a massive buzz doing it, you just need to reduce the chances of getting hurt thats all. You will get hurt, so allow for it.