I suggest that you select long lasting Shabbat candles that can burn for a few hours, and light them with a meaningful ceremony at the correct time, i.e. at least 18 minutes before sunset. When your husband arrives home, together you can inaugurate the Shabbat holiness, perhaps meditate on the Shabbat lights, and then sing Shalom Aleichem, Kiddush and the other Shabbat rituals.
Your question can be separated into two sections: what is the Reform position on when candles ought to be lit, and what can one do if your situation does not allow the candles to be lit by that time. Let's address both of these issues.
According to Mark Washofsky's Jewish Living: A Guide to Contemporary Reform Practice, “technically, Shabbat starts at the onset of 'night' of Friday night, but precisely when does this moment come? The uncertainties over this question led to the establishment of a requirement 'to add from the weekday to the holy day,' that is, to begin Shabbat sometime before nightfall on Friday...” (pg 75) His response reflects the traditional practice of lighting candles before dark.
In many homes the custom is for one family member to light candles at their prescribed time, regardless of whether any other members of the family have yet gathered. Others may be on the road coming home or may be at the synagogue, but the candles get lit in their own time.
Your question suggests a different value; that is, the importance of lighting the candles together and ushering in Shabbat as a sacred family event. For you, and many others, this moment of gathering is a high value. When family schedules do not allow everyone to arrive home before sunset, a conflict arises between the value of lighting candles in their time and lighting the candles as a sacred family event.
Were I in conversation with you discussing this conflict I would suggest several steps to find a comfortable resolution. First, this conflict offers an opportunity for the family to discuss these conflicting values. Acknowledging the values on all sides of the question allows you as a family to decide consciously which values take precedence in your home. Secondly, I would ask if there are any scheduling adjustments that can be made to accommodate Shabbat in a different way. Third, if scheduling cannot be adjusted and the family consensus is that you value lighting the candles as a family, I would go one step further to consider all the ways you can deepen your Shabbat observance.
The Reform approach values individual autonomy. This is an opportunity for you to find the ways to bring our classic tradition into conversation with your lived 21st century lives. Your desire to create a meaningful Shabbat observance within your household is admirable. I wish you much good luck, and Shabbat Shalom.