Video formats for an iPad First Generation?

Hi! I made a video of a family event and my father wants to put it on his first generation iPad. Unfortunately, he is due for an upgrade and I don’t want to update his OS since he will loose some stuff he will need on his trip. The video is an MP4, is there an older format I should try to convert it to that iTunes will let me upload? My copy of iTunes won’t let me copy the MP4 over.