The practices that you mention – exchanging wedding bands and kissing your wife on the lips – are lawful in and of themselves. Regarding the ring, however, you should have your ring made of something other than pure gold. The woman's can be of gold.
These practices, though they might be at variance with the wedding traditions that you personally are familiar with, are harmless. You may honor these local customs.
As for the fact that the people in that society are predominantly Christians, this does not mean you have to refrain from honoring their non-religious customs. Sometimes, it is better to observe those customs to avoid difficulties or to bring about positive outcomes.
Ibn Taymiyah makes this clear in his book entitled Iqtidâ' al-Sirât al-Mustaqîm
. He writes (176):
If a Muslim lives in a non-Muslim country, regardless of whether or not that country is hostile with the Muslim countries, he will not be obligated to make himself appear different than them. This is on account of the difficulties that doing so can pose. Indeed, it might become preferable or even obligatory for him to conform to their outward practices if there is a benefit for the faith in doing so like inviting them to Islam, or preventing hardship for the Muslims, or for realizing any other wholesome intention.
In this case, your observing these harmless local customs is desirable, since it brings benefits to your marriage. It endears your wife to you, who is a convert to Islam, and since these customs are not unlawful in and of themselves, such endearment is desirable. It also prevents unnecessary discomfort for her with her family and avoids future problems between you and your in-laws.
And Allah knows best