The only big caution I offer is that make sure you're having a good time and not feeling pressured to perform. THat will only make orgasm more elusive. However, I know of many women in the 50s and 60s who pursue very active, almost daily, sex with their partners. Menopause can both depress sexual desire and increase it. Nothing makes sex work better than more sex.
Anal sex is something that many people experiment with briefly, but few continue it for long.
If, however, she's curious but fearful then here are some suggestions. Use your finger to anally stimulate her while you kiss or have oral sex, or even during intercourse. Be sure to be hygenic, don't insert something in the anus and then into the vagina, as bacteria can cause problems. The anus was not designed for the rigors of intercourse. The tissues are easily torn, causing anal fissures and hemmoroids.