I would like the thoughts and opinions of married Christians as to whether or not to use toys as a fun add-on to regular sexual intimacy. What are some pitfalls or habits that may be red flags? How does this increase holiness and godliness? Should this be a thing that should be avoided or allowable?
Has she said why she wants to introduce these? Does she indicate dissatisfaction with sex currently, or is this more of a desire to just change things up?
75 percent of women require additional stimulation to reach [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse].
https://www.psychologytoday.com/us/blog/all-about-sex/200903/the-most-important-sexual-statistic
A vibrator that focuses in the right area in conjunction with intercourse, or after intercourse, can help with this issue for some, though there are other methods as well
Also there have been some studies, though limited, regarding possible implications of the introduction of a vibrator in particular. Most of the material could relate to other types as well. You can find this article online, but I will not link to it because it has material that may be a problem for some. It looked at possible concerns with the introduction of a vibrator for women in a relationship. It primarily relates their experience in the following areas:
Six recurring concerns emerged: (i) change in orgasmic patterns; (ii) fear of using an outside, “unnatural”object; (iii) dependency; (iv) entitlement; (v) reaction of partners; and (vi) changes in sexual attitudes
Changes in a Woman’s Sexual Experience and Expectations Following the Introduction of Electric Vibrator Assistance
Beyond these areas recognized in secular sources, some churches (Catholic for instance) teach that you must be open to life in sexual interactions with your spouse. They also discuss what constitutes a valid marital act. This would be something to look into in that case.
As to whether it promotes mutually giving of yourself to each other, that could well depend on the motivations, uses, etc..
It might be good to have a discussion together of what you think the one flesh relationship of marriage entails, what the nature of married sexuality is in general, and then see how this impacts that.
By the way, while not everyone would agree with this conclusions, an interesting read to generate discussion about the nature of sex from a religious perspective is John Paul II's Theology of the Body
John Paul II's Theology of the Body