Is it fine to mix tretinoin .1% with jergens lotion so I can apply it evenly on face?

Retin-A or Retinols need to be right near the surface of clean skin.  A moisturizer, particularily an occulsive type, will prevent Vitamin A derived products from penetrating the skin.  In general, patients should apply therapeutic and thin products first and occlusive and thicker products last.  (i.e. thin to thick).  Use your Vitamin A products first and follow with your moisturizer.

Since you are asking this question, it seems obvious that you have not consulted a physician who specializes in skin rejuvenation. Retina-A should be used with a number of other skin care products to achieve your desired result. Moisturizer or lotion are not 2 of them. They add weight to the skin and only increase the appearance of crinkles and wrinkles. Additionally, they block the Retin-A from getting to the deeper cells where it can work to improve the skin. What you need is a non irritating cleanser with an alpha hydroxyl to remove the outer dead cell layer to brighten the skin and remove a barrier from Retin-A penetration, a pH balancer/antioxidant like Vitamin C Serum, the Retin-A to build collagen and reduce the scars and crinkles and a zinc oxide sun block to prevent further UVA damage (SPF does not indicate UVA protection). Though your skin will be dry for a while, it will start making its own moisture again. (See PlasticSurgeryToday.com/beautifulskinlaserresurfacinghighlandsnorthcarolina/obagi-nu-derm/)