Yes, holiday first, provided it won't exacerbate your MH condition.
I must admit I've only been to Center Parks once, with Ex and DC, and I'm afraid it was not the best holiday I've ever had - self catering is not my ideal for a restful holiday, and many of our holidays had to be self-catering to keep costs down.
But I can see the attraction of Center Parks if you're a sporty family 
I've been on a fair few different antidepressants over the years, and have always been told to take them in the morning. The only side effects I've ever had with SSRIs (paroxatine, sertaline, escitalipram) were slight nausea at the very start of being prescribed this type of meds. Am old, so it wasn't till 1998, shortly after it was approved, that I even began them.
The meds I took previous to that worked by the numbing the emotions. I tried them a couple of times, but ended up deciding I would prefer to feel miserable than to feel nothing 
For me, SSRIs were very effective, very quickly. Everyone's physiology is slightly different though, so sometimes you have have several goes at finding the right one, giving it the recommended 6 weeks before you evaluate your MH to see if it has improved.
You may wonder if they were so effective why I've been on several different ones. Quite simply, because I got better again and came off them. But the next time life got me down (crap marriage) I would need them to recover my mood.