Leaving the boyfriend out of things...?

It's been a while since i've been on here... things have been going pretty well! But I am now in need of some more advice if anyone is kind enough to offer it:

I've been with my boyfriend for about 15 months now, and we've been really happy together. Being together has been easy, and we've always openly discussed a future together in quite serious terms - discussing locations to live that work with our jobs/studies and planning ways to do this.

We've recently hit our first major disagreement... He had made it clear that he didn't want to go on a holiday with me (+ my friend) this year as he couldn't afford it due to starting a university course that he can't get any loans for (unusual situation in the UK, not sure how things are done in the USA). He was however, happy for us to go. So with discussions with my friend, we found a great idea for a holiday just us two in Thailand where we get to work up close with elephants; feeding, cleaning, and playing with them - an experience of a life time. :icon_bigg

He didn't like that plan at all, however. He feels like he would be being left out and said that he would never even have thought of doing something so exciting without me and wants to share these kind of experiences with me. He thinks that if I do it, it'll show i'm immature, careless with money (i'm more of the opinion that I should have fun while I can in the few years i'm at university and have money available, and be frugal when I'm leaving home), and not caring enough about him. :icon_sad:

Don't get me wrong, I would love to do this with him, but it's not possible at the moment, and I would have to wait 6 years to be able to do so with him (he's starting medicine). And of course in that time we might not be able to go due to time and/or money. I don't wan't to look back on my life and think that I missed out on such a great experience? :bang:

What do you guys think - am I being cruel by not instantly backing off the idea, or should I try and have these experiences while i'm young?

TLDR: Me and my friend looked at going to thailand to work with elephants, my boyfriend reacted very badly to the idea and thinks we should be doing things that exciting together, but can't actually do so for another 6 years due to his finances. What should I do!?