In the pic it looks like two 1" holes and three 3/4" holes.
If that's the case I'd plan on using one of the 1" holes for your drain. I'd probably use the other as the intake for the closed loop and use the 3/4" holes as the outlets.
One precaution in that scenario - it might be a good idea to put a 90 degree elbow pointed down on the closed loop intake to keep it from sucking air at the surface.
The drain line setup looks fine to me, but unless you plan to restrict the drain with the valve (which can be risky unless the system is designed to handle a clogged drain) it's not really necessary.
On the return pump sketch the valve and union are mixed up - reverse that. They're also usually closer to the pump (usually as close as practical) so you don't have to remove all that piping when you need to take the pump out for maintenance/replacement.
I like having a valve and union on my drain also. You never know what will come along. The valve should be on the tank side of the union, weather it is the drain or return. Like Chris said put the valve and union close to the pump. If you are going to put them on the drain put them close to the tank.