I'm sure he'll be fine. If you have time to introduce them, that would make it an easier on both sides. The most important thing at this point is that they are fed nightly and old dishes removed next day prior to them waking (morning is best). Even if your baby missed three weeks of play, I'm certain once upon your return and after continuing routine he would be fine. Mine have gone longer without out of cage play at times, sadly, but are fine. But if you have a friend who will get him out for play, then that would be best, especially if he is alone.
BTW, how exciting, have a safe trip!