You have posted in the wrong forum - Kitesurfing / General would get more responses. You should post there just in case someone has a different view to me.

We often get 25+ days, esp. at the start of the season but not enough to warrant the smaller kite only. The summer pattern is that by about 2pm the seabreeze is approx 15-18 knots. Where it goes from there depends on how hot it is and other variables. It can crank right up to 25knots sometimes it drops off. (Sometimes we get 15k easterlies for 2 weeks and everyone gets sh1tty )

The best I can say is that the majority of days will be about 18-22 knots. Even if it really cranks up, there often will be some part of the day when you could get out. The river will be an option if the coast is going off too much.

The season usually starts with a bang and everyone runs out and gets smaller kites for XMAS only to find the wind strength not getting much above 20-22 knots in the New Year.

My advice would be to bring both kites if you could as you will get a longer season - maybe push it out to 7 months. Alternatively, there is a an active 2nd hand market and you can often get pristine kites a few years old for $500 or less, so, whatever you do decide, it wont be a do-or-die decision, you have plenty of fallbacks.

Good winds.