Becca,
I would study the best practices of large 401k (403b) and mimic those plans.
The largest in the world and best 401k plan has all of its allocation plans for all age targeted plans on line by asset class.
You can view it on
Home | Thrift Savings Plan. The thrift savings plan was started in 1984 when Federal employees were shifted from a solid pension plan to a weak one with a 401k. It is free of all political influence. The other element of success for TSP is low operating cost. Vanguard investments comes the closest to this commercially