wow, just caught up on this thread, and wow!
My opinion, if you care. If $300 is going to make or break a 10 day Disney trip, then yes, you better rethink everything. I would not change any plans except cancellation for $300.
Since you now have the payment extended and work will be okay, then I am glad for you.
We've taken a vacation every year for the last 5 or 6 years, actually last year I got the beach AND DW so that was very exciting, BUT that also means this year funds aren't quite there (of course building a 26 x 32 garage doesn't help) but there is no vacation for us this year. sometimes it just works out like that.