Rachel, I wouldnt get too set in your tour guide ideas. Most hotels book with certain tour companies BECAUSE they have offered professional reliable service to their prior guests. I'll never forget the guy who told me he was going out diving with "Jose". Told me how "Jose" was going to save him $10 a tank over what our guide was charging. Well, once he got out on the boat, "Jose" told him that he forgot to tell him he had to buy gas. $120 later, he gets to the dive site to find that his tank is only half full. It's just like the US...you get what you pay for. This guy ended up paying more for his "discount" dive than our dive shop charges. He did the rest of his diving with our shop.
Your hotel has a vested interest in seeing that you have a good time no matter what tour you go on because ultimately, they will reap the benefits (by word of mouth) of your having a great vacation. Conversely, if they send you on tours that dont show up or dont deliver on what they promise, it tends to sour your entire trip, including your hotel even though it may be a fine place.
I'm just suggesting that you give the hotel an opportunity to tell you what they offer before you make a final decision. Most tour companies that offer the same tours have the same or very near the same pricing.