Basic economy seats already assigned

Hi all. We just booked a round trip flight fwa-clt-muc. Family of 4 with two tweens. We didn’t pick seats during booking, expecting we might later.

Now when looking at our reservations we all have seats assigned. Decent ones even.

Question is… now that we have seats assigned. Is there a risk of losing them and getting stuck on a 10hr flight with crummy or separated seats? Are they solid?

Thanks! Chris