If I understand the business context for these domains correctly, they refer to 2-year old and 4-year old racing horses.
With such a specialized niche, you really have to take into consideration the size of the market and the interent usage for the market (how much the net is used and how much business is transacted through the net).
I'm not very familiar with horse racing, so I'm not in a position to give you a strong opinion without a lot of further research in the area.
As for a "ballpark" sort of estimate, I'd say any final sales price you can get for this kind of domain that falls in the $1000-$5000 range should probably be satisfactory.
For a sale under $1000, factor in your need to sell, your buyer's resources and motivation (as best as you can estimate), how domain-needy your niche market is, and proceed accordingly.
Good luck with your sale.
Note to board: yet another case where extensive domain market data would greatly help establish the right price.