Your home videos are region free off course, so as such it's just a matter of whether their viewing equiptment can support whatever format you burn and send the DVD's in.
Computers can of course play both PAL and NTSC videos. Many modern DVD players can also do this. Some will even have the ability to convert the NTSC signal to PAL or vice versa. Again, it all depends on what your relatives intend to use to view these DVD's and how you burn them.
The standard in the states is NTSC. So burning your DVD's as such would be your best bet for compatibility.
Also, your thread has been moved to the General Chat area, being that it is a non-web design topic.