We tried back at the end of November to plant eco-lawn seed in our back yard. It has grown, but VERY slowly, and very patchy. I know we could give it more time and it will eventually grow, but we have a 2-year old son who is dying to get outside and play in the yard, and our grass areas have been fenced off with chicken wire for 4 months now. We're going to put in a fescue blend sod, and I'm wondering the following: Do we HAVE to remove the grass that has already started growing?

Here's a couple pieces of info to note:
1. We tilled the entire yard very well prior to seeding, obviously the ground has settled since then
2. We don't mind if the eco-lawn ends up coming through the new sod and taking over down the road, we like that grass but we're ready for a full lawn sooner rather than later
3. The grass that has come in so far is no more than maybe a 1/2" above the soil, so it's not very established yet

Advice will be helpful!