How many years are you willing to wait for a pool of shade that covers the entire seating area for many hours per day? Because if you don't buy and plant a tree that is quite big from the start it's not going to do the job for a long time.

I'm not expecting any tree to provide shade at high noon. I assumed that a multi trunk tree would have a wider spread, but less dense. It's for long term, but I'm not opposed to spending a little extra for a larger gallon pot.

if you want shade within the next decade .. imo... you are looking at ball and burlap stock.. not a couple more gallon pot ... and easily talking of spending hundreds more ...

plus all teh attendant risk and cost of buying and planting HUGE stock ...

with trees we talk of tree time.. counted in decades ... so make sure your dreams and plans take that into account ... reality ...

if it were me.. i would design some type of pergola or shade cloth structure for the immediate shade ... AND plant the smaller trees.. so that by the time the structure needs to come down.. the trees are ready to take over ...

ken

ps: and yes.. it doesnt escape me... that the cost of the top will exceed the huge trees ..

You seem to have a mental picture of the effect you want. I'd go to a good nursery and look at their stock and see what appeals.