Left hanging for transportation belize city

Landed last night in Belize city with arrangements for a private rental car today. Driver never showed up despite us speaking on phone and seemingly all set.

We know there's a bus system from Belize city but are racibg a few issues with this change. We have carryon suitcases and backpacks- worried how and where they'll go if we try the crowded bus. Heard about a shuttle that does a few stops from the airport- not sure if it's the international airport or the local one we are currently right beside. Can't find info on contact or pricing for that shuttle. We were really hoping to not pay for a traditional rental as it cuts into our budget a lot. Hence finding one through marketplace- unfortunately learning the hard way now.

If we get to SI- are there (name/cost) local resort or tourist shuttles that could get us up to and help set up a border crossing so we can get to Tikal?

Also how about shuttles- or car sharing between SI and Placencia? And then Placencia to Belize City? We won't need a car in Placencia but need to get back to Belize City after 4 days.

Suggestions? Can we piggyback off resorts shuttles for a cost? Any suggestions help ❤️