Looks like a pretty expensive bike ride.
Note: the only rail connection that gets you to Hohenschwangau before the ticket kiosk opens (8 AM) leaves Munich at 4:48 AM and gets to the Hohenschwangau bus stop at 7:32. That would cost the full fare of 26,70€ per adult one way (is everyone an adult?).
The next connection leaves Munich at 6:53 and gets to Hohenschwangau at 9:13. It might take 10 minutes to walk to the kiosk and you need to pick up tickets one hour before tour time, so you could take a 10:30 tour. That trip would cost the same thing 26,70€ each.
BTW, that's the cost of the train fare to Füssen Bahnhof only. However, the 6:53 connection gets you to Füssen at 8:55 and the bus leaves after 9 AM, so if you already had a Bayern-Ticket for your return (purchased the day before or that morning at the Hbf), you could use it for the bus to Hohenschwangau.
If you already have the Bayern-Ticket in hand and you purchase full fare tickets from Munich to Kaufbeuren at 18,30€/adult, you can leave on the 7:53 train from Munich. That train gets to Kaufbeuren at 8:48 and leaves at 9:00, when the Bayern-Ticket is valid. It gets to Füssen at 9:56 and the bus gets you to the bus stop in Hohenschwangau at 10:13. You could schedule your tour for about 11:30.
I think you need to schedule your tour time in advance at www.hohenschwangau.de.