Theres nothing that says you cant have one of Tim or Tiago on the court at all times if they start the game together.. its definately manageable.
1st Q
6 minutes - Sub in Blair for Tiago
2 minutes - Sub in Tiago for Tim
2nd Q
12 minutes - Sub in Bonner for Blair
5 minutes - Sub in Tim for Tiago
2 minutes - Sub in Blair for Bonner
Tim - 30 minutes
Tiago - 30 minutes
Bonner - 18 minutes
Blair - 18 minutes
If Matty is playing well and hitting his 3's as he has been lately.. there are extra minutes available at the expense of Blair. Plus they will play the majority of their minutes against bench players.
30 minutes each may be ecessive for Tim and Tiago during the regular season.. so you may have to go a 2 or 3 minutes stretch with Blair and Bonner provided they can match up against bench bigs during that time. Or perhaps try some small ball with Leonard at the 4.. considering playing Bonner and Blair at the 4 is pretty much small ball anyway due to lack of rebounding/defense and general size.