Honey Bee World

So, my successful over-wintered hive is a 3 Deep. It is still wrapped, not insulated. Huge amounts of Aspen and willow pollen coming in this past week, lots of wax cappings showing up at bottom reduced entrance.
I want to split this hive at end of April, it's too big to manage as a three deep.
My concern is that I will find brood in all 3 boxes. Should I stress over this or just wait to see what the situation really is?
If brood in all 3 boxes, should I just shake all of top bees down, put in Queen excluder, put top box back on, then after nurses move up, move to new spot. Add new queen 2 days later?
Advice on options are all welcome. I know there are many.
In November top box was 10 frames of honey. Bees using top entrance hugely to bring in pollen now.

I should add, I have drawn comb and honey frames from my February dead-out. Resources for expansion. Making lemonade when life handed me lemons, I hope

It depends on what your goals are, and how you intend to split.

Are you trying for maximum honey production? Are you just wanting more hives? Are you buying a mated queen to introduce, or are you going to allow the bees to raise their own new queen?

Personally, if I were in your shoes, the easiest thing would be to wait until you had drones, and then do a walkaway split. Simply make sure there were eggs in both halves and place the two splits side by side. (Or if you find the queen, move the box with the queen to a new location in the beeyard, and leave the weaker half of the split in the old location to collect all the foragers.)

If you are introducing a mated queen, your method of putting in a queen excluder for 4 or 5 days, and then giving the queenless half the new queen will work just fine.

There's tons of different ways to do this, and all of them will work just fine.

Of course, if maximum honey production was your goal, I would make 3 splits of equal strength, and introduce 2 mated queens to the 2 queenless splits. I would put a queen excluder on each single with supers above. At the end of the season, they could be combined back together for wintering, or could be overwintered individually.

CB, thank you for the reply. I am torn between wanting honey and more bees. I was hoping for some happy medium. Leave the big hive strong enough to max out the main flow (we get two, most years I understand)
and have a new colony that builds up enough to overwinter.
Now you have me thinking hard about your last idea, a triple split. That would work great!
Thanks again,
Brian