Visiting with 3 month old--altitude an issue?

Voxel

Just wondering if anyone has family or friends who have travelled with a baby to Big Sky from a low elevation and if the altitude was an issue at all. We live at sea level and our baby would be 3 months old. It is approximately 7000 feet at the base of Big Sky if I'm not mistaken. One pediatrician said it would be fine, the other was wary. Anyone have family or friends who have brought their baby for a visit and can provide input?