I depends on the required ground cover you are looking for before allowing use. A spring seeding of tall fescue/blue is a tough one. The blue grass is at a great disadvantage due to the 30 or so days it takes for germination. the tall fescue germinates quickly but the inevitable warm weather will stifle development. Additionally, tall fescue has poor wear tolerance in its early stages of development since most of its benefits are derived from a deep root system which is non existent early on. Your best bet is effective watering and fertilization to get the best possible results in the shortest amount of time. I would plan on reseeding this fall if the field is used. I would also advise topdressing of 1/8" or so with a topdressing compatible with your own soil just prior to use. My experience has shown that topdressing at this time helps to protect the crowns of the young pants and minimize damage. Obviously you will have to be very concerned with soil moisture when allowing play. A wet field will be far more susceptible to damage than the same on a mature stand of turf.