You should take a plane, because 1) it’s a lot safer and 2) there’s more chances that there won’t be a minyan on the boat, and 3) A lot of the boats look the same, so not necessarily are you on the same one they were on.
And also, where does it say that you have to daven with a minyan? If that was true, then if there was no minyan then that means you shouldn’t daven. But I have seen people daven by themselves (in the farm, etc.
Also, even if you wouldn’t daven, I don’t think you should deprive your family of a vacation because of your chumarot. I once heard in a shiur that you’re not supposed to be chumrot on other people, and that is also prohibited to do that.
Also, If you’re a man, and your going on vacation make sure to bring along your tephillin. I know many cases personally when someone who wears tephillin every day, forgot to bring them on vacation, by mistake- and it wasn’t even my fault, because it is not like clothing or food that is instinctual to pack along. It is very important to bring them along with you. And not to forget.
Also, very important is that make sure there is kosher food when you are there. Sometime you get there and you’re tierd and lo and behold, you end up eating whatever they serve. So be very carefull with that.
Also, when you are there, there is gorgeous scenery.
When I went to a different island, many people told me to take advantage of the scenery and use it to further your spiritual growth. You should meditate there, or else all that you see, the handiwork of g-d can be lost upon you. Which would be very unfortunate.
Also, you should say tefilat hadereck (a prayer for a safe journey)- even though nowadays it really isn’t a journey, nevertheless you should say it.