@Yamazaki @The Harbinger of Ferocity @AristoI will begin, withholding my post, on the grounds of a challenge that I am not attempting to bluff the elves in question owing to the fact I am not lying. I am intentionally neglecting to withhold the information that if they do choose to fight, that we are ready for them; something they can reasonably expect.
I undertake your argument. While I do not necessarily see this as a diplomacy check on the basis that it appears to me Geraint it attempt to sow confusion into the minds of the enemies and stave off attack - I will heed your roll and agree that you have made a diplomacy check rather than my assumption that you meant a bluff check. However, my results remain unchanged. These creatures are considered hostile and a 13 just won't do it in this situation. Next time, I will bring the discussion here rather than make that assumption. That was poor DMing on my part. Once again, I chalk this up to adapting to the change in medium.
Building from this, unless Jaegar explicitly goes against what seems to be the rest of the group's intent to withhold openly engaging, there shouldn't be too much issue. If you would rather they just fight us for the sake of an encounter, that is another matter altogether and I will just withdraw my claim.
My initial response would be to say yes, it is Jaegar's desire to explicitly go against the group's intent. In elaboration for two reasons. First off, it is in his character at least during this juncture as Sander's Reach is his home and these creatures are allegedly endangering the livelihood of the people. His decisions may be quite rash during this initial dungeon crawl. Second, is a DM-move (for lack of a better term) that I suppose works better when playing at the table. When the pace begins to slow down and the party isn't exactly in the swing of things (which while you are not to blame, @Aristo and @Yamazaki are showing only minimal interest at this point) I like to move things along and bring a bit more excitement.) Typically, this can be something like a random encounter or an NPC making potentially poor decisions to move the party along for better or worse. Often times, my table top group would adapt a deck of playing cards to illicit this effect. (I.e., you've taken to long to decide or play actively pick a card and see what happens.) Something I may have to dial back in this instance, especially if it is a turn off for the group.
On another note, one positive is that the elves should only have a surprise round - their initiative (even on a 20, as initiative cannot fumble or critical) is behind that of the tiger's.
This is a bit of a faux pas on my fault. I agree that standard 3.5 does not account for a nat 20 or nat 1 on an initiative roll. However, something I should have mentioned in the beg poinning, a nat 20 or nat 1 is always a pass or fail respectively regardless of modifiers. So a nat 20 during the initiative check is automatically number 1 on the list. Subsequently, a 1 on any check is always a fail. On another note, such rolls typically have additional positive or negative effects on the situation. For example, if a PC rolls a nat 20 on a disguise check the results may include that the disguise works so well that a debt is repaid to that player or a smith's journeyman mistakenly delivers some sort of special weapon to the PC.
However!!!! Because of my own misstep I will abide by the standard 3.5 rules for this encounter. The tiger will fight first. Because the elves have not hit anyone, it won't really interfer with anything. So I won't be changing my post at all. But just know that in the future nat 20's and nat 1's mean something in this adventure. With the exeption of the initiative rolls - if nat 20s or 1s are rolled subsequent in this encounter I will treat them as I typically do - we will just ignore the initiative portion for now.
Sorry for the confusion.