Some small issues
Let others tell you what to do - no need for the additional to
What clothes did you decide on for him?
I decided on the mountain boots for Max
Generally we use decide in the past tense unless asking about a timeframe for a decision eg will you decide what to do about this by next week or if asking if a decision is possible eg can you decide what to do.
If you ask/talk about the outcome of a decision as in your examples then the decision has already happened and is therefore in the past tense.
I hope this makes sense to you