A few thoughts:
1. It is important to be *very* clear to your donors on where the money raised goes. Blurring the line into having folks believe they are assisting a charity when they are funding your vacation seems suspect.
2. Easiest to avoid co-mingling funds. For example, 100% of fund X goes to the charity and 100% of fund Y goes to bike trip expenses.
3. An easy way both you and your donors can see that 100% of fund X is going to the charity is to link directly to their pages (some let you be an affiliate type that tracks totals but otherwise goes directly to them), rather than having to hand over funds.
I've seen folks who have solicited 100% of funds raised goes to a particular cause they care about and the bike trip is one more way to get publicity. I say hats off to them in that case. I've also seen "charity rides" such as the MS150 or American Red Cross type rides where the organization at least has a financial accounting (990T) type and it is known there are expenses for cycling but riders are expected to raise X$ to participate. I've also met some folks on a "bike and build" (
https://bikeandbuild.org/) where they raised funds and also contributed sweat equity. In general I don't have a big issue with these types when a substantial portion ends up going to charitable purposes.
Where I see more problems is the small scale folks without clear transparency or funding, perhaps a paypal or gofundme type campaign and there is a blurring of expenses as well as not clear transparency to account for funds raised. I think that causes a problem for the donor (you can't deduct charitable donation if not clearly to a charitable organization) as well as is an easy avenue for fraudulent behavior where the charity becomes the "bait" to solicit funds but really lions share is funding a vacation.