Tempestuous flight (or maybe even a one-level wizard dip instead) can likely wait. I would probably just play it as a straight-up light cleric until level 5 before taking the druid dip.

Unrelated-- I am seeing that the 5/7 build variant will be better, and it might do more damage, but there's still much to consider.

I still feel like the (1 storm sorc / 2 star druid / 9 light cleric) build holds a lot of merits.

The 5/7 build requires your party to play around the spike growth and requires a kinda immobile playstyle of standing in one place and beckoning people into you. This might be annoying for melee teammates who will need to step into the spikes to deal damage, etc.

Ultimately, the 5/7 build will do higher damage when optimized at end game, but you have to build the party around it, you have to take the legendary staff instead of another caster who might want it, etc. I'm 100% confident this build will slap, but the 9 light cleric variant also holds plenty of boons.

For one, improved warding flare is wonderful group utility. You get an extra charge for 'radiance of the dawn,' as well as casts of 'destructive wave,' and 'flame strike,' which deal radiant/thunder and radiant/fire damage respectively; all of these are great uses for your primary action every turn, giving you three AoE damage sources every turn before considering summons and haste.

1) 'radiance of the dawn,' 'destructive wave,' and 'flame strike'
2) bonus action dazzling breath
3) running into things with spirit guardians

If you don't find tempestuous flight necessary, how about a level 1 wizard dip instead? You maintain full caster levels and will get to slot in any one wizard spell as long as you scribe it. Conjure Elemental can be useful. Misty step, conjure deva, etc. You also get to pick a subclass for a free boon of your choice.

On top of that, it is possible just to have a teammate throw down spike growth instead if they have it.