It's very expensive, especially for a large group, but I have always wanted to do the Keys to the Kingdom behind the scenes tour ($116 value one day admission and then an extra $99 for the five hour tour) -- one part is to see the tunnels under the MK. Anyway, we have a large group (12) coming down for a wedding in March. It's a big enough group that I figure everyone can do their own thing and my mom and I (just the two of us from our party) are going to do it.
If interested, I think a tour like this would be a great thing to do solo. Here is the website:
https://disneyworld.disney.go.com/events-tours/magic-kingdom/keys-to-the-kingdom-tour/
The Wild Africa Trek that another poster mentioned looks cool too. It's not a thing I've always wanted to do, though like KTTK, so it would be really tough for me to justify the price. As I only do one Disney park per trip I have the $100 plus admissions vs. a lower admission per day for people who get the longer multi day tickets on top of the cost of any tour, making a tour a pricey proposition.
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What has kept me from doing KTTK in the past (why I see it as such a great solo option)
-- I waited till my son turned 16, so he could do it with me (he is my Orlando buddy - with me on most trips), but found he didn't really want to do the tour (was afraid it would spoil the magic). And though he would do it with me, he really likes just a regular day at the MK better, so that would mean doing two MK days on one trip (something I don't want to do).
-- DH would do it with me, but would really just prefer to skip all theme parks period. For the wedding he is just coming down the Thursday before -- family activities on Friday (nature park picnic in area) and Saturday wedding and flying home on Sunday. The rest of us will come down for a week before (Saturday till following Sunday).
-- Often I am down with a large group, so go with the flow of what the whole group does.
-- Often if I suggest things for the large group -- I pay as I am in a better financial position than most of the extended family. That, though, means I am budget conscious about what I choose, as multiple thing by six to 10 and you are talking big dollars. Something like KTTK would bust my budget.
-- Then finally I had a last minute trip last November where it would work, but alas the tours were sold out, so a little advanced planning is needed.
-- I am reserving my spot early (this September for me and my mom) and doing it in March (It's been on my list to do for about 10 years). My mom who is coming with me too, is in a good financial position and will pay her own way and would pay for me if I'd let her.
-- I also usually pick splurges that others in my immediate family would really enjoy and be interested in. This is a rare item where only I am interested.